chore: upgrade to 7.3.0+v1.154.0

- matrixdotorg/synapse: v1.149.1 -> v1.154.0
- pgautoupgrade/pgautoupgrade: 17-alpine -> 18-alpine (+ PGDATA pin for in-place upgrade)
- ghcr.io/element-hq/matrix-authentication-service: 1.14.0 -> 1.18.0
- nginx: 1.29.6 -> 1.31.1
- discorddb postgres: 13-alpine -> 16-alpine (conservative bump; manual dump/restore required)

Deferred to separate PR:
- mautrix/signal v0.8.7 -> v26.02.2 (CalVer; requires signaldb dump/restore)
- mautrix/telegram v0.15.3 -> v0.2605.0 (CalVer; requires telegramdb dump/restore)
- signaldb/telegramdb postgres: 13-alpine (deferred with bridges)

.env.sample

@@ -105,7 +105,7 @@ ENABLE_REGISTRATION=false
 SERVE_SERVER_WELLKNOWN=false
 
 # Serve /.well-known/matrix/{server,client} on SERVER_NAME via Traefik.
-# Can be used when SERVER_NAME != DOMAIN and SERVER_NAME is served by Traefik.
+# Can be used when SERVER_NAME is other than DOMAIN and SERVER_NAME is served by Traefik.
 #COMPOSE_FILE="$COMPOSE_FILE:compose.wellknown.yml"
 
 ALLOW_PUBLIC_ROOMS_FEDERATION=false
@@ -149,7 +149,6 @@ ENCRYPTED_BY_DEFAULT=all
 #SESSION_LIFETIME=60d
 #TRACK_PUPPETED_USER_IPS=true
 
-
 ## Room complexity limit (prevents joining large remote rooms that cause DB bloat)
 ## complexity ≈ state_events / 500. Default 100.0 blocks rooms with >50000 state events.
 #ROOM_COMPLEXITY_LIMIT=100.0
@@ -248,7 +247,6 @@ RETENTION_MAX_LIFETIME=4w
 ## Web Client (Redirect)
 #WEB_CLIENT_LOCATION=https://element-web.example.com
 
-
 ## State compression (reduces database bloat from federation)
 ## Runs synapse_auto_compressor daily, built from source on first start
 #COMPOSE_FILE="$COMPOSE_FILE:compose.compress-state.yml"

compose.discord.yml

@@ -30,7 +30,7 @@ services:
       - internal
 
   discorddb:
-    image: postgres:13-alpine
+    image: postgres:16-alpine
     secrets:
       - discord_db_password
     environment:

compose.yml

@@ -128,9 +128,9 @@ services:
     secrets:
       - db_password
     environment:
-      # postgres:18 relocated the default PGDATA to /var/lib/postgresql/18/docker.
+      # postgres:18 relocated default PGDATA to /var/lib/postgresql/18/docker.
-      # Pin it to the legacy path so pgautoupgrade finds the existing cluster on the
+      # Pin to legacy path so pgautoupgrade finds the existing cluster and
-      # mounted volume and upgrades it in place, instead of init'ing an empty one.
+      # upgrades in place instead of init-ing an empty one.
       - PGDATA=/var/lib/postgresql/data
       - LC_COLLATE=C
       - LC_CTYPE=C