feat: add postgres 16 for synapse (local disk, C collation) ahead of MAS

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

compose/hf-pdocker-01/matrix/docker-compose.yml

@@ -1,20 +1,20 @@
 services:
   synapse:
-    image: matrixdotorg/synapse:latest
+    # 2026-08-20: matrixdotorg repo is abandoned (froze at 1.148.0); upstream is now element-hq.
+    # Pinned deliberately so the running version is visible in the file - bump manually.
+    image: ghcr.io/element-hq/synapse:v1.159.0
     container_name: synapse
     restart: unless-stopped
     environment:
       - SYNAPSE_SERVER_NAME=mess.hobbs.farm
       - SYNAPSE_REPORT_STATS=no
     volumes:
-      - /mnt/docker-data/configs/matrix/data:/data
+      # 2026-08-20: moved off NFS -> local NVMe (SQLite locking, Known Issue #16)
+      - /var/lib/synapse:/data
     ports:
       - "8008:8008"
     networks:
       - matrix-internal
-    depends_on:
-      synapse-db:
-        condition: service_healthy
     mem_limit: 1G
     memswap_limit: 1G
     healthcheck:
@@ -52,21 +52,22 @@ services:
         max-file: "3"
 
   synapse-db:
-    image: postgres:15-alpine
+    image: postgres:16-alpine
     container_name: synapse-db
-    user: "1024:100"
     restart: unless-stopped
     environment:
       - POSTGRES_USER=synapse
-      - POSTGRES_PASSWORD=synapse
+      - POSTGRES_PASSWORD=MnLASftPXou9ubOmawmALYwROwgM
       - POSTGRES_DB=synapse
+      # C collation is MANDATORY - Synapse refuses any other
       - POSTGRES_INITDB_ARGS=--encoding=UTF-8 --lc-collate=C --lc-ctype=C
     volumes:
-      - /mnt/docker-data/databases/matrix-db:/var/lib/postgresql/data
+      # LOCAL disk, never NFS (Known Issue #16). No user: 1024:100 - that is an NFS workaround.
+      - /var/lib/synapse-db:/var/lib/postgresql/data
     networks:
       - matrix-internal
-    mem_limit: 256M
-    memswap_limit: 256M
+    mem_limit: 512M
+    memswap_limit: 512M
     labels:
       - "com.centurylinklabs.watchtower.enable=false"
     healthcheck: