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/lldap/metadata.json

@@ -62,5 +62,5 @@
       "generate": true
     }
   ],
-  "notes": "Web UI at http://<host>:17170 — log in with 'admin' and your admin password. LDAP endpoint is ldap://lldap:3890 (base DN dc=homelab,dc=local). Create users and groups here; Authelia authenticates against them."
+  "notes": "Web UI at http://<host>:17170 — log in with 'admin' and your admin password. lldap's web UI has no OIDC, so if you expose it through nginx-proxy-manager, protect it with Authelia forward-auth (auth_request block in the proxy host's Advanced tab — see nginx-proxy-manager notes). LDAP endpoint is ldap://lldap:3890 (base DN dc=homelab,dc=local). Create users and groups here; Authelia authenticates against them and issues OIDC/SSO sessions from the same directory."
 }