fix(email): render conditionals, localise password placeholders, fix caller/template variable drift

Bundle of email-renderer and email-caller fixes triggered by a
reproducer on picpeak.nothaft.cloud (gallery_created mail showing
literal `{{#if welcome_message}}` markers and `Passwort: (set at
creation)`). The audit that followed surfaced six more user-visible
defects in the same surface; all are fixed here so customer-facing
mail renders cleanly.

Renderer (`backend/src/services/emailProcessor.js`)

- `safeTemplateReplace` now resolves `{{#if VAR}}…{{/if}}` blocks
  before flat `{{var}}` substitution. The shipped templates have used
  Handlebars-style conditionals since migration 026; the renderer
  ignored them, so the markers leaked verbatim into every mail with
  an empty welcome_message. Lifted to module scope and exported so
  the conditional contract is unit-testable. Single-pass, non-nested
  (commented).

- Added `passwordSetAtCreationI18n` next to the existing two i18n
  password sentinels so `(set at creation)` (sent by the publish-
  from-draft flow when only the bcrypt hash remains) is localised
  to "Das bei der Erstellung der Galerie gesetzte Passwort" /
  equivalent in EN/DE/NL/PT/RU instead of the raw English string.

- Added an opt-in `{ escapeHtml: true }` mode to `safeTemplateReplace`
  so admin-supplied free text (`event_name`, `host_name`, …) is
  HTML-escaped on substitution into the HTML body. Allowlist of
  passthrough keys (`welcome_message` already-HTML, server-generated
  URLs `gallery_link` / `client_link`). Subject and text body keep
  the legacy unescaped behaviour. `formatWelcomeMessage` now escapes
  before nl2br so the welcome_message allowlist is safe.

- New `htmlToText()` strips `<style>` and `<script>` blocks (and
  their content) before tag-stripping, decodes common entities, and
  collapses whitespace. Used by the textBody fallback in
  `sendTemplateEmail` — without this, every template missing a
  `body_text` produced a "plain-text" mail starting with the 100+
  lines of CSS embedded by `wrapEmailHtml()`.

- The client-access section (#172) now mirrors its HTML block into
  `textBody` using the same per-language strings, so plain-text
  recipients see the link / PIN / warning. `pinLabel = 'PIN'` moved
  into `clientAccessI18n` (RU uses ПИН-код).

- Added `getSupportEmail()` exported helper that reads
  `branding_support_email` from `app_settings` (JSON-decoded), with
  the SMTP from-address as fallback. Used by the gallery_expired and
  archive_complete callers below.

- Removed dead `require('handlebars')` (unused since the regex
  renderer landed; pre-existing lint error in this file).

Callers (data the templates already reference)

- `expirationChecker.js queueExpirationWarning`: send `expiry_date`
  (templates use this, the old code sent `expiration_date` —
  typo'd key, never read), drop the hard-coded `.de`/`en` sniff
  (the processor formats with the recipient's resolved language),
  add the `{{password_security_message}}` sentinel for
  `gallery_password` (plaintext is gone by warning time, so
  customers used to see literal `{{gallery_password}}` in the mail).

- `expirationChecker.js handleExpiredEvent`: both queueEmail calls
  now supply `host_name`, `event_date`, `expiry_date`,
  `support_email` so the EN/DE/NL/PT/RU `gallery_expired` template
  doesn't render literal `{{host_name}}, your gallery expired on
  {{expiry_date}}`. Skip the duplicate admin send when
  admin_email == customer_email.

- `archiveService.js`: `archive_complete` queue now supplies
  `host_name`, `photo_count` (from `photoEntries.length`),
  `archive_date`, `support_email` — the previous payload had only
  `event_name` and `archive_size`, so most of the mail was
  unfilled placeholders.

Tests

- `__tests__/services/emailProcessor.safeTemplateReplace.test.js`:
  16 cases — flat substitution, conditional truthy/falsy/missing/
  multi-line/sibling/numeric-0, plus 5 cases for the new
  `escapeHtml` option (default off, escape on, allowlist
  passthrough for welcome_message and gallery_link).

- `__tests__/services/emailProcessor.htmlToText.test.js`: 7 cases —
  the regression scenario (full wrapped body with embedded `<style>`
  block), tag-stripping, entity decoding, paragraph spacing.

- `__tests__/utils/formatters.test.js`: 12 cases for `escapeHtml`,
  `nl2br`, and the now-escaping `formatWelcomeMessage`.

35 cases total, all green. Lint clean on every touched file
(also fixes a pre-existing `no-prototype-builtins` warning in the
process). Pre-existing failures in
`__tests__/services/backupService.enhanced.test.js` are unrelated
and pre-date this branch.

backend/__tests__/services/emailProcessor.htmlToText.test.js

@@ -0,0 +1,75 @@
+/**
+ * Unit tests for emailProcessor.htmlToText.
+ *
+ * Regression: when a template ships without a body_text, sendTemplateEmail
+ * used `htmlBody.replace(/<[^>]*>/g, '')` to derive the plain-text fallback.
+ * That regex strips angle-bracket tags but leaves the *contents* of <style>
+ * and <script> blocks intact — so any HTML wrapped by wrapEmailHtml() (which
+ * embeds a 100+ line <style> block) produced a "plain-text" email starting
+ * with `body { margin: 0; padding: 0; … }`. htmlToText fixes that.
+ */
+
+jest.mock('../../src/database/db', () => ({ db: jest.fn() }));
+
+const { htmlToText } = require('../../src/services/emailProcessor');
+
+describe('htmlToText', () => {
+  it('returns empty string for empty input', () => {
+    expect(htmlToText('')).toBe('');
+    expect(htmlToText(null)).toBe('');
+    expect(htmlToText(undefined)).toBe('');
+  });
+
+  it('strips <style> blocks and their contents', () => {
+    const html = '<html><head><style>body { margin: 0; color: red; }</style></head><body>Hello</body></html>';
+    const out = htmlToText(html);
+    expect(out).toBe('Hello');
+    expect(out).not.toMatch(/margin/);
+    expect(out).not.toMatch(/color/);
+  });
+
+  it('strips <script> blocks and their contents', () => {
+    const html = '<body><script>alert("x")</script>Hi</body>';
+    expect(htmlToText(html)).toBe('Hi');
+  });
+
+  it('converts <br> tags to newlines', () => {
+    expect(htmlToText('a<br>b<br />c<BR/>d')).toBe('a\nb\nc\nd');
+  });
+
+  it('keeps a paragraph break between adjacent <p> tags', () => {
+    expect(htmlToText('<p>one</p><p>two</p>')).toBe('one\n\ntwo');
+  });
+
+  it('decodes the common HTML entities', () => {
+    expect(htmlToText('Tom &amp; Jerry &lt;3 &quot;hi&quot;'))
+      .toBe('Tom & Jerry <3 "hi"');
+  });
+
+  it('handles a fully-wrapped email body without leaking CSS rules', () => {
+    // Shape mirrors what wrapEmailHtml() produces: a <style> block with many
+    // CSS rules followed by the actual content.
+    const wrapped = `
+<!DOCTYPE html>
+<html>
+<head>
+  <style>
+    body { margin: 0; padding: 0; font-family: sans-serif; background-color: #f5f5f5; }
+    .email-container { max-width: 600px; }
+    .button { background-color: #5C8762; color: white !important; }
+  </style>
+</head>
+<body>
+  <h2>Galerie erfolgreich erstellt</h2>
+  <p>Liebe(r) Natalie,</p>
+</body>
+</html>`;
+    const out = htmlToText(wrapped);
+    expect(out).toContain('Galerie erfolgreich erstellt');
+    expect(out).toContain('Liebe(r) Natalie');
+    expect(out).not.toMatch(/margin/);
+    expect(out).not.toMatch(/font-family/);
+    expect(out).not.toMatch(/background-color/);
+    expect(out).not.toMatch(/\.button/);
+  });
+});

backend/__tests__/services/emailProcessor.safeTemplateReplace.test.js

@@ -0,0 +1,138 @@
+/**
+ * Unit tests for emailProcessor.safeTemplateReplace.
+ *
+ * Covers the two regressions that hit picpeak.nothaft.cloud on the
+ * 3.32.x betas:
+ *   - {{#if VAR}}…{{/if}} blocks rendered as literal text in the email
+ *     because the renderer only handled {{var}} substitution and the
+ *     shipped templates use Handlebars-style conditionals.
+ *   - {{var}} substitution inside a kept conditional block.
+ *
+ * The publish-from-draft password localisation lives inside the wider
+ * processTemplate() pipeline (DB-backed), so it isn't covered here — the
+ * sentinel string '(set at creation)' is asserted only at the i18n-map
+ * level by integration in adminEvents.js.
+ */
+
+jest.mock('../../src/database/db', () => ({ db: jest.fn() }));
+
+const { safeTemplateReplace } = require('../../src/services/emailProcessor');
+
+describe('safeTemplateReplace', () => {
+  describe('flat variable substitution', () => {
+    it('replaces {{var}} with the variable value', () => {
+      expect(safeTemplateReplace('Hello {{name}}!', { name: 'Paul' }))
+        .toBe('Hello Paul!');
+    });
+
+    it('leaves unknown variables untouched', () => {
+      expect(safeTemplateReplace('Hello {{name}}!', {}))
+        .toBe('Hello {{name}}!');
+    });
+
+    it('coerces non-string values to string', () => {
+      expect(safeTemplateReplace('Count: {{n}}', { n: 42 }))
+        .toBe('Count: 42');
+    });
+
+    it('handles empty templates and missing variables map', () => {
+      expect(safeTemplateReplace('', { x: 1 })).toBe('');
+      expect(safeTemplateReplace('plain text', undefined)).toBe('plain text');
+      expect(safeTemplateReplace(null, {})).toBe(null);
+    });
+  });
+
+  describe('{{#if VAR}}…{{/if}} blocks', () => {
+    it('strips the block when the variable is missing', () => {
+      const tpl = 'before {{#if welcome}}HELLO {{welcome}}{{/if}} after';
+      expect(safeTemplateReplace(tpl, {})).toBe('before  after');
+    });
+
+    it('strips the block when the variable is an empty string', () => {
+      const tpl = 'before {{#if welcome}}HELLO {{welcome}}{{/if}} after';
+      expect(safeTemplateReplace(tpl, { welcome: '' })).toBe('before  after');
+    });
+
+    it('strips the block when the variable is null', () => {
+      const tpl = '{{#if x}}kept{{/if}}';
+      expect(safeTemplateReplace(tpl, { x: null })).toBe('');
+    });
+
+    it('keeps the block and substitutes inside it when truthy', () => {
+      const tpl = 'before {{#if welcome}}HELLO {{welcome}}{{/if}} after';
+      expect(safeTemplateReplace(tpl, { welcome: 'world' }))
+        .toBe('before HELLO world after');
+    });
+
+    it('handles multi-line conditional blocks', () => {
+      const tpl = [
+        'Liebe(r) {{host_name}},',
+        '',
+        '{{#if welcome_message}}',
+        'Persönliche Nachricht:',
+        '{{welcome_message}}',
+        '{{/if}}',
+        'Galerie-Details:',
+      ].join('\n');
+
+      const withMsg = safeTemplateReplace(tpl, {
+        host_name: 'Natalie',
+        welcome_message: 'Schön, dass ihr da seid!',
+      });
+      expect(withMsg).toContain('Persönliche Nachricht:');
+      expect(withMsg).toContain('Schön, dass ihr da seid!');
+      expect(withMsg).not.toContain('{{#if');
+      expect(withMsg).not.toContain('{{/if');
+
+      const withoutMsg = safeTemplateReplace(tpl, {
+        host_name: 'Natalie',
+        welcome_message: '',
+      });
+      expect(withoutMsg).not.toContain('Persönliche Nachricht');
+      expect(withoutMsg).not.toContain('{{#if');
+      expect(withoutMsg).not.toContain('{{/if');
+      expect(withoutMsg).toContain('Liebe(r) Natalie,');
+      expect(withoutMsg).toContain('Galerie-Details:');
+    });
+
+    it('handles multiple sibling conditionals independently', () => {
+      const tpl = '{{#if a}}A{{/if}}|{{#if b}}B{{/if}}|{{#if c}}C{{/if}}';
+      expect(safeTemplateReplace(tpl, { a: 1, c: 'yes' })).toBe('A||C');
+    });
+
+    it('treats numeric 0 as falsy', () => {
+      expect(safeTemplateReplace('{{#if n}}has-n{{/if}}', { n: 0 })).toBe('');
+    });
+  });
+
+  describe('HTML escaping (escapeHtml: true)', () => {
+    it('does not escape by default', () => {
+      const tpl = 'Welcome to {{event_name}}';
+      expect(safeTemplateReplace(tpl, { event_name: 'Test <script>' }))
+        .toBe('Welcome to Test <script>');
+    });
+
+    it('escapes admin-supplied values when opted in', () => {
+      const tpl = 'Welcome to {{event_name}}';
+      expect(safeTemplateReplace(tpl, { event_name: 'Test <script>alert(1)</script>' }, { escapeHtml: true }))
+        .toBe('Welcome to Test &lt;script&gt;alert(1)&lt;/script&gt;');
+    });
+
+    it('escapes both the < > and & characters and quotes', () => {
+      expect(safeTemplateReplace('{{x}}', { x: '<a href="evil">A & B\'s</a>' }, { escapeHtml: true }))
+        .toBe('&lt;a href=&quot;evil&quot;&gt;A &amp; B&#39;s&lt;/a&gt;');
+    });
+
+    it('passes welcome_message through unescaped (already HTML from formatWelcomeMessage)', () => {
+      const tpl = '<p>{{welcome_message}}</p>';
+      expect(safeTemplateReplace(tpl, { welcome_message: 'Hi<br />there' }, { escapeHtml: true }))
+        .toBe('<p>Hi<br />there</p>');
+    });
+
+    it('passes server-generated URLs through unescaped', () => {
+      const tpl = '<a href="{{gallery_link}}">link</a>';
+      expect(safeTemplateReplace(tpl, { gallery_link: 'https://example.com/g/abc?token=xyz&u=1' }, { escapeHtml: true }))
+        .toBe('<a href="https://example.com/g/abc?token=xyz&u=1">link</a>');
+    });
+  });
+});