Docker: read every setting from a .env file

Each folder gets a .env.example listing every homeserver, admin panel
and web client setting with its default (empty means the default).
Compose reads .env for ports, registry and the PostgreSQL password, and
passes it to the containers through env_file; the compose files keep
only the database driver, connection string and internal addresses.
.env is git-ignored.

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

Docker/docker-compose.postgresql.prod.yml

@@ -2,8 +2,8 @@
 # PostgreSQL, each in its own container, pulled from a registry.
 #
 #   cd Docker
-#   WARP_SERVER_NAME=matrix.example.org WARP_POSTGRES_PASSWORD=change-me \
-#     docker compose -f docker-compose.postgresql.prod.yml up -d
+#   cp .env.example .env      # then edit it; set WARP_POSTGRES_PASSWORD
+#   docker compose -f docker-compose.postgresql.prod.yml up -d
 #
 # Homeserver http://localhost:8008, admin panel http://localhost:8009, web
 # client http://localhost:8080. PostgreSQL is reachable only on the compose
@@ -51,13 +51,10 @@ services:
     entrypoint: ["/bin/sh", "-c"]
     command:
       - test -f /data/signing.key || warp generate-keys --output /data/signing.key; exec warp serve
+    env_file: .env
     environment:
-      WARP_SERVER_NAME: ${WARP_SERVER_NAME:-localhost}
-      WARP_WELL_KNOWN_CLIENT_BASE_URL: ${WARP_PUBLIC_BASEURL:-http://localhost:8008}
       WARP_DB_DRIVER: postgres
       WARP_DB_CONNECTION_STRING: postgres://warp:${WARP_POSTGRES_PASSWORD:?set WARP_POSTGRES_PASSWORD}@postgres:5432/warp?sslmode=disable
-      WARP_REGISTRATION_ENABLED: ${WARP_REGISTRATION_ENABLED:-false}
-      WARP_FEDERATION_ENABLED: ${WARP_FEDERATION_ENABLED:-false}
     volumes:
       - warp-data:/data
     ports:
@@ -69,6 +66,7 @@ services:
     restart: unless-stopped
     depends_on:
       - warp
+    env_file: .env
     environment:
       WARP_ADMIN_HOMESERVER: http://warp:8008
     ports:
@@ -80,6 +78,7 @@ services:
     restart: unless-stopped
     depends_on:
       - warp
+    env_file: .env
     environment:
       WARP_WEB_HOMESERVER: http://warp:8008
     ports: