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/config/transcription.js

@@ -0,0 +1,68 @@
+import { log } from './logger.js';
+
+/**
+ * Recording transcription / AI summarization integration.
+ *
+ * When the per-room "recording transcript" setting is enabled, Redlight POSTs
+ * to ${TRANSCRIPTION_API_URL}/prompt with header `X-Api-Key: ${TRANSCRIPTION_API_KEY}`
+ * as soon as the "video" format of a recording becomes available (delivered via
+ * BBB's recording-ready callback). Leave both env vars empty to disable the
+ * integration entirely.
+ */
+
+const TRANSCRIPTION_API_URL = process.env.TRANSCRIPTION_API_URL || '';
+const TRANSCRIPTION_API_KEY = process.env.TRANSCRIPTION_API_KEY || '';
+
+const DEFAULT_PROMPT = 'Summarise the key decisions made in this meeting.';
+
+export function isTranscriptionEnabled() {
+  return !!(TRANSCRIPTION_API_URL && TRANSCRIPTION_API_KEY);
+}
+
+/**
+ * Request a summary/transcript for a recording. Never throws — failures are
+ * logged and reported via the boolean return value.
+ *
+ * @param {object} opts
+ * @param {string} opts.meetingId   Room UID / BBB meeting ID
+ * @param {string} opts.recordingId BBB record ID
+ * @param {string} [opts.prompt]    Optional custom prompt
+ * @returns {Promise<boolean>} true if the request was accepted
+ */
+export async function requestTranscription({ meetingId, recordingId, prompt }) {
+  if (!isTranscriptionEnabled()) {
+    log.server.warn('Transcription request skipped: TRANSCRIPTION_API_URL or TRANSCRIPTION_API_KEY is not configured');
+    return false;
+  }
+
+  const base = TRANSCRIPTION_API_URL.endsWith('/') ? TRANSCRIPTION_API_URL : `${TRANSCRIPTION_API_URL}/`;
+  const url = new URL('prompt', base).toString();
+
+  try {
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'X-Api-Key': TRANSCRIPTION_API_KEY,
+      },
+      body: JSON.stringify({
+        prompt: prompt || DEFAULT_PROMPT,
+        meeting_id: meetingId,
+        recording_id: recordingId,
+      }),
+      signal: AbortSignal.timeout(15_000),
+    });
+
+    if (!response.ok) {
+      const body = await response.text().catch(() => '');
+      log.server.error(`Transcription request failed: status=${response.status} body=${body.slice(0, 200)}`);
+      return false;
+    }
+
+    log.server.info(`Transcription requested for recording ${recordingId} (meeting: ${meetingId})`);
+    return true;
+  } catch (err) {
+    log.server.error(`Transcription request error: ${err.message}`);
+    return false;
+  }
+}