multistreaming: scenes/composition, installer build support, service updates

- multistreaming (new): RTMP ingest + multi-platform fan-out with pluggable providers (Twitch/YouTube/Kick/custom), zero-knowledge key vaults, Authelia OIDC auth, shared rooms with editor/streamer roles, single-use invites, per-account streaming grants, and scenes & composition (grid/PiP layouts, text/image overlays, per-output audio routing).
- installer: support Dockerfile build in metadata (not just image) and RSA key generation for the Authelia OIDC JWKS.
- authelia: add OIDC provider with portainer + multistreaming clients (public + PKCE).
- services: remove allprox; add nginx-proxy-manager and portainer; update lldap; regenerate catalog.

services/multistreaming/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "multistreaming",
+  "version": "1.0.0",
+  "description": "Self-hosted service: ingest one RTMP feed from OBS and restream it to multiple platforms/channels.",
+  "type": "commonjs",
+  "main": "src/index.js",
+  "scripts": {
+    "start": "node src/index.js"
+  },
+  "engines": {
+    "node": ">=18"
+  },
+  "dependencies": {
+    "express": "^4.21.2",
+    "node-media-server": "^2.7.4"
+  }
+}