fix(crm): self-heal missing CRM email templates at boot + recover queue

The CRM template seeders (crmEmailTemplates / contractEmailTemplates /
eventReminderTemplates) were idempotent and ready, but only
contractEmailTemplates was actually called (lazily, by contractService
sends). crmEmailTemplates had no caller anywhere — every install that
didn't pre-exist its templates failed every quote_sent / invoice_sent /
storno_issued / invoice_reminder_* send with "Email template '<key>'
not found". The queue processor retries 3 times then leaves the row
in status='pending', retry_count=3, silently dead with no admin
surface (see project_crm_backlog for the eventual System Health page).

Fix: wire all three seeders into server.js startServer() right before
startEmailQueueProcessor. The new _emailTemplateBoot.js orchestrates
all three and then, for any template_key it just inserted, resets
retry_count on stuck email_queue rows of that email_type so the
queue processor's next tick picks them back up. Recovery is targeted:
unrelated retry-exhausted rows (e.g. SMTP-timeout failures) are not
touched.

Integration test boots a fresh CRM DB, pre-seeds a stuck quote_sent
row plus an unrelated stuck row, runs the boot helper, and asserts:
templates landed, stuck quote_sent row was reset, unrelated row was
left alone.

Already-deployed installs heal automatically on the next backend
restart after this lands.

backend/server.js

@@ -777,6 +777,16 @@ async function startServer() {
     
     // Initialize email transporter and start queue processor
     await initializeTransporter();
+    // Seed CRM / contract / event-reminder email templates and recover
+    // any queue rows that exhausted retries because their template
+    // didn't exist yet. Runs once per boot via module-level caches in
+    // each seeder. See _emailTemplateBoot.js for the full rationale.
+    try {
+      const { seedEmailTemplatesAndRecoverQueue } = require('./src/services/_emailTemplateBoot');
+      await seedEmailTemplatesAndRecoverQueue(db, logger);
+    } catch (err) {
+      logger.warn('Email template self-heal failed at boot:', err.message);
+    }
     startEmailQueueProcessor();
     
     // Start webhook delivery worker (#327)