feat(gallery): info banner above the photo grid (#932) (#1063)

* feat(gallery): info banner above the photo grid (#932)

A short informational note rendered at the TOP of a gallery, above the
photos. Distinct from the promotional banner (#440), which stays by the
footer for marketing copy — the reporter's case is an onboarding hint ("use
the menu button to filter"), which is useless below a gallery the guest has
to scroll past first.

Mirrors the promo feature's shape rather than inventing a second one: a
global default in Settings → Branding (branding_info_markdown) plus a
per-event inherit/custom/off override. Markdown via the existing
MarkdownContent sanitiser — no raw HTML, no CSS injection. Empty global
default means nothing renders, so upgrading changes nothing visible.

Deliberately NOT included: an alignment knob (this is short helper copy, not
marketing layout) and guest dismissal — the issue lists dismissal as a
nice-to-have, and it needs per-guest persistence that is its own decision.

Migration 176 is idempotent (hasColumn / existing-key guarded).

Note on the payload plumbing: the per-event fields travel in the /photos
response, not just /info. GalleryAuthContext seeds its cached event from the
gallery LOGIN response — a small identity subset — so anything absent there
is undefined right after a guest signs in. /photos is the payload that
refreshes on every gallery load, which is why the fields were added there
and why GalleryView reads them from `data.event`. Verified in a browser
across all three modes; reading them from the context event instead silently
collapsed every override back to 'inherit'.

* fix(branding): map branding_info_markdown on read so saving can't wipe it (#932)

External review caught this. BrandingSettings declared no info_markdown and
formatBrandingSettings never mapped branding_info_markdown, so BrandingPage's
hydration — setBrandingSettings(prev => ({ ...prev, ...formatted })) — kept
the empty-string initializer instead of the persisted value. The form loaded
blank and the next Save posted '' back, wiping a configured banner. Silently:
the gallery keeps rendering the old copy until that save lands.

This is the same bug the footer/promo fields hit in #441 + #440 / #460, which
the read mapper still carries a comment about. Add the field to the interface
and the mapper, and pin the round-trip for the whole editable branding set so
the next field added is caught by a test rather than by a user losing copy.

Verified: the new test fails 3/4 with the mapper line removed.

* fix(gallery): honour the info-banner override in the reveal-hidden view (#932)

External review, round 2. The hidden-until-reveal branch renders GalleryLayout
with the context `event`, which is seeded from the gallery login response and
carries no banner fields — so while a gallery was hidden, a per-event 'off'
silently resolved to 'inherit' and the global banner appeared on a gallery the
admin had muted.

Resolve the fields there the same way the main render path does. The two
full-page layouts (gallery-premium, gallery-story) are deliberately left alone:
they return before GalleryLayout and render no header, footer or promo banner
either — injecting a wrapper into layouts documented as having 'their own
integrated UI' would be a design change, not a fix.

---------

Co-authored-by: Paul Nothaft <[email protected]>

backend/migrations/core/176_gallery_info_banner.js

@@ -0,0 +1,78 @@
+/**
+ * Migration: gallery info banner (#932)
+ *
+ * A short informational message rendered ABOVE the photo grid, so guests see
+ * it on load. Distinct from the promotional banner (#440), which sits by the
+ * footer and stays there for marketing/CTA copy — the reporter's case is an
+ * onboarding hint ("use the menu button to filter"), which is useless below a
+ * gallery the guest has to scroll past first.
+ *
+ * Deliberately mirrors the promo columns rather than inventing a second
+ * shape: a global default in branding settings plus a per-event
+ * inherit/custom/off override. Same semantics, same normalisation, so the
+ * two banners stay predictable next to each other.
+ *
+ * Idempotent (hasColumn / existing-key guarded) so a re-run or a
+ * partially-applied state is safe.
+ */
+
+exports.up = async function (knex) {
+  // 1. events.info_mode — 'inherit' (use the global default) | 'custom'
+  //    (this event's own copy) | 'off' (no banner for this gallery).
+  const hasInfoMode = await knex.schema.hasColumn('events', 'info_mode');
+  if (!hasInfoMode) {
+    await knex.schema.alterTable('events', (table) => {
+      table.string('info_mode', 16).notNullable().defaultTo('inherit');
+    });
+    console.log('  added events.info_mode (default "inherit")');
+  } else {
+    console.log('  events.info_mode already exists, skipping');
+  }
+
+  // 2. events.info_markdown — per-event copy, only read when mode = custom.
+  const hasInfoMarkdown = await knex.schema.hasColumn('events', 'info_markdown');
+  if (!hasInfoMarkdown) {
+    await knex.schema.alterTable('events', (table) => {
+      table.text('info_markdown').nullable();
+    });
+    console.log('  added events.info_markdown (nullable text)');
+  } else {
+    console.log('  events.info_markdown already exists, skipping');
+  }
+
+  // 3. The global default, following the existing `branding_<name>`
+  //    convention used by the promo rows this mirrors. Empty string = the
+  //    banner is off everywhere until an admin fills it in, so upgrading
+  //    changes nothing visible for existing installs.
+  const infoSetting = {
+    setting_key: 'branding_info_markdown',
+    setting_value: JSON.stringify(''),
+    setting_type: 'branding',
+  };
+  const exists = await knex('app_settings').where('setting_key', infoSetting.setting_key).first();
+  if (!exists) {
+    await knex('app_settings').insert({ ...infoSetting, updated_at: knex.fn.now() });
+    console.log('  added branding_info_markdown (empty = banner off)');
+  } else {
+    console.log('  branding_info_markdown already exists, skipping');
+  }
+
+  console.log('Migration 176_gallery_info_banner completed');
+};
+
+exports.down = async function (knex) {
+  console.log('Rollback: 176_gallery_info_banner');
+
+  if (await knex.schema.hasTable('events')) {
+    if (await knex.schema.hasColumn('events', 'info_markdown')) {
+      await knex.schema.alterTable('events', (table) => table.dropColumn('info_markdown'));
+    }
+    if (await knex.schema.hasColumn('events', 'info_mode')) {
+      await knex.schema.alterTable('events', (table) => table.dropColumn('info_mode'));
+    }
+  }
+
+  if (await knex.schema.hasTable('app_settings')) {
+    await knex('app_settings').where('setting_key', 'branding_info_markdown').del();
+  }
+};