Group voice and video calls with MatrixRTC and LiveKit

Every call in the web client now goes through MatrixRTC with a LiveKit
SFU, the model Element Call and Element X use; the legacy 1:1 m.call.*
calls are gone. In a room of two the other person is rung and can answer
or decline; in a bigger room a banner offers to join the call. Calls show
a grid of participant tiles with mute, camera, screen sharing and leave,
and media is end-to-end encrypted in encrypted rooms.

Server:
- MSC4140 delayed events (send/state with a delay, plus the
  delayed_events list/restart/cancel/send API), stored and scheduled, so
  a member whose client drops off is taken out of the call.
- POST /user/{userId}/openid/request_token, which lk-jwt-service uses to
  hand out LiveKit tokens.
- org.matrix.msc4143.rtc_foci in /.well-known/matrix/client, configured
  under client_api.rtc.
- Room presets let members send call membership state.
- Migration 0014 for both SQL dialects.

Deploy: LiveKit and lk-jwt-service in compose (calls.yml) and the helm
chart. Docs: docs/calls.md, configuration and deployment.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy/compose/docker-compose.yml

@@ -12,6 +12,12 @@
 # http://localhost:8009; with the web profile, the web client is on
 # http://localhost:8080.
 #
+# For voice and video calls (LiveKit and its JWT service) add calls.yml:
+#
+#   docker compose -f docker-compose.yml -f calls.yml --profile web up -d
+#
+# WARP_PORT moves the homeserver off host port 8008.
+#
 # Create the first administrator once the server is up:
 #
 #   docker compose exec warp warp create-account --username admin --admin
@@ -63,7 +69,7 @@ services:
     volumes:
       - warp-data:/data
     ports:
-      - "8008:8008"
+      - "${WARP_PORT:-8008}:8008"
 
   # The admin panel is optional. Start it with the admin profile:
   #   docker compose --profile admin up -d