feat: add AI summary / transcript integration for recordings

Ported from greenlight-tm: when TRANSCRIPTION_API_URL and
TRANSCRIPTION_API_KEY are set in the .env and the per-room
"AI summary / transcript" setting is enabled, Redlight POSTs to
${TRANSCRIPTION_API_URL}/prompt (header X-Api-Key) as soon as the
"video" format of a recording becomes available.

- transcription.js: service with env gating, timeout and logging
- bbb.js: pass meta_bbb-recording-ready-url on meeting create when the
  room has the setting enabled
- recordings.js: unauthenticated /recording-ready callback that
  verifies BBB's signed_parameters JWT (HS256, shared secret), caches
  the recording and requests the transcription once per recording
  (deduped via transcript_requested_at)
- rooms: new recording_transcript column, accepted on create/update
- branding endpoint exposes transcriptionEnabled so the UI only shows
  the toggle when the server is configured
- RoomDetail: toggle under "Allow recording" (disabled when recording
  is off), de/en i18n
- chore: bump version to 2.4.0

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/routes/recordings.js

@@ -1,7 +1,9 @@
-import { Router } from 'express';
+import { Router, urlencoded } from 'express';
+import jwt from 'jsonwebtoken';
 import { authenticateToken } from '../middleware/auth.js';
 import { getDb } from '../config/database.js';
 import { log } from '../config/logger.js';
+import { isTranscriptionEnabled, requestTranscription } from '../config/transcription.js';
 import {
   getRecordings,
   getRecordingByRecordId,
@@ -9,6 +11,8 @@ import {
   publishRecording,
 } from '../config/bbb.js';
 
+const BBB_SECRET = process.env.BBB_SECRET || '';
+
 const router = Router();
 
 /**
@@ -176,6 +180,65 @@ async function fetchAndSyncRecordings(meetingID, fallbackName) {
   }
 }
 
+// POST /api/recordings/recording-ready - BBB recording-ready callback (unauthenticated)
+// BBB posts `signed_parameters`, a JWT signed with the shared BBB secret.
+// Fires once per playback format; the transcription request is only sent when
+// the "video" format first becomes available and the room has the setting on.
+router.post('/recording-ready', urlencoded({ extended: false }), async (req, res) => {
+  try {
+    const signed = req.body?.signed_parameters;
+    if (!signed || typeof signed !== 'string') {
+      return res.status(400).json({ error: 'signed_parameters is required' });
+    }
+
+    let payload;
+    try {
+      payload = jwt.verify(signed, BBB_SECRET, { algorithms: ['HS256'] });
+    } catch {
+      return res.status(403).json({ error: 'Invalid signature' });
+    }
+
+    const recordId = payload.record_id;
+    const meetingId = payload.meeting_id;
+    if (!recordId || !meetingId) {
+      return res.status(400).json({ error: 'record_id and meeting_id are required' });
+    }
+
+    // Always answer 200 from here on so BBB does not keep retrying —
+    // "nothing to do" is a valid outcome for this callback.
+    const db = getDb();
+    const room = await db.get('SELECT id, uid, name, recording_transcript FROM rooms WHERE uid = ?', [meetingId]);
+    if (!room || !room.recording_transcript || !isTranscriptionEnabled()) {
+      return res.json({});
+    }
+
+    const rec = await getRecordingByRecordId(recordId).catch(() => null);
+    if (!rec) return res.json({});
+
+    const formatted = formatBbbRecording(rec, room.name);
+    const hasVideo = formatted.formats.some(f => f.type === 'video');
+
+    // Cache the recording so the dedupe marker below has a row to live on
+    await upsertRecording(db, formatted);
+
+    if (!hasVideo) return res.json({});
+
+    // Dedupe: BBB fires the callback once per format
+    const cached = await db.get('SELECT transcript_requested_at FROM recordings WHERE record_id = ?', [recordId]);
+    if (cached?.transcript_requested_at) return res.json({});
+
+    const ok = await requestTranscription({ meetingId, recordingId: recordId });
+    if (ok) {
+      await db.run('UPDATE recordings SET transcript_requested_at = CURRENT_TIMESTAMP WHERE record_id = ?', [recordId]);
+    }
+
+    res.json({});
+  } catch (err) {
+    log.recordings.error(`Recording-ready callback error: ${err.message}`);
+    res.status(500).json({ error: 'Error processing recording-ready callback' });
+  }
+});
+
 // GET /api/recordings - Get recordings for a room (by meetingID/uid)
 router.get('/', authenticateToken, async (req, res) => {
   try {