Enable lab media_pipelines in composed config and wire ac-ms-media-transcode.

Overlay media pipeline PHP/JS/SQL on compose, nginx HLS location, enable
feature in lab config.php, and ensure media storage dirs on BE nodes.

Co-authored-by: Cursor <cursoragent@cursor.com>

sim/cluster0/scripts/compose-lab-backend.sh

@@ -94,6 +94,40 @@ overlay_lab_seed_src() {
 }
 overlay_lab_seed_src ShortLinksRepository.php
 overlay_lab_seed_src UrlShortenerDatabase.php
+overlay_lab_seed_src MediaPipelinesRepository.php
+overlay_lab_seed_src MediaPipelineRunner.php
+
+overlay_lab_seed_api() {
+  _f="$1"
+  if [ -f "${LEGACY}/public/api/${_f}" ]; then
+    log "overlay lab-seed api ${_f}"
+    mkdir -p "${COMPOSED}/public/api"
+    cp -a "${LEGACY}/public/api/${_f}" "${COMPOSED}/public/api/"
+  fi
+}
+overlay_lab_seed_api media_pipelines.php
+
+overlay_lab_seed_public() {
+  _rel="$1"
+  if [ -f "${LEGACY}/public/${_rel}" ]; then
+    log "overlay lab-seed public/${_rel}"
+    mkdir -p "${COMPOSED}/public/$(dirname "$_rel")"
+    cp -a "${LEGACY}/public/${_rel}" "${COMPOSED}/public/${_rel}"
+  fi
+}
+overlay_lab_seed_public assets/js/media_pipelines.js
+overlay_lab_seed_public index.php
+
+overlay_lab_seed_sql() {
+  _f="$1"
+  if [ -f "${LEGACY}/sql/migrations/${_f}" ]; then
+    log "overlay lab-seed sql/migrations/${_f}"
+    mkdir -p "${COMPOSED}/sql/migrations"
+    cp -a "${LEGACY}/sql/migrations/${_f}" "${COMPOSED}/sql/migrations/"
+  fi
+}
+overlay_lab_seed_sql 081_media_pipelines.sql
+overlay_lab_seed_sql 081_media_pipelines.sqlite.sql
 
 overlay_api ac-ms-identity
 overlay_api ac-ms-rbac
@@ -253,9 +287,30 @@ return [
             ],
         ],
     ],
+    'media_pipelines' => [
+        'enabled' => true,
+        'developers_only' => true,
+        'script_root' => '${WS}/ac-ms-media-transcode',
+        'storage_root' => '/var/www/ac/media-pipelines',
+        'hls_url_prefix' => '/app/androidcast_project/media/hls',
+        'hls_filesystem_root' => '/var/www/ac/media-pipelines/hls',
+        'logo_path' => '${WS}/ac-ms-media-transcode/assets/pirate_drift.png',
+        'ytdlp_enabled' => true,
+    ],
 ];
 PHP
 
+MEDIA_ROOT="/var/www/ac/media-pipelines"
+MEDIA_HLS="${MEDIA_ROOT}/hls"
+MT_ROOT="${WS}/ac-ms-media-transcode"
+log "ensure media-pipelines dirs ${MEDIA_ROOT}"
+mkdir -p "${MEDIA_HLS}" "${MEDIA_ROOT}/pipelines"
+chown nginx:nginx "${MEDIA_ROOT}" "${MEDIA_HLS}" 2>/dev/null || true
+if [ -d "${MT_ROOT}/bin" ]; then
+  chmod +x "${MT_ROOT}"/bin/*.sh 2>/dev/null || true
+  log "media-transcode scripts at ${MT_ROOT} (logo: ${MT_ROOT}/assets/pirate_drift.png)"
+fi
+
 BUILD_CFG="${WS}/ac-be-builder/config/config.php"
 if [ -f "${COMPOSED}/config/config.php" ]; then
   log "write ac-be-builder config.php (shared cluster session + DB)"