feat(544): shipped compose files run on the orchestrator's defaults; the app waits for its database itself

Brings the three compose files in line with rule 198 (milestone 544,
step 6203, at the operator's request):
- no healthcheck on the app or the database, so a slow pg_isready on
  stalled storage can no longer get a working database killed;
- no deploy.restart_policy in the Swarm file, so Swarm's default
  (condition: any) restarts clean exits too, instead of on-failure with
  max_attempts leaving the app down;
- depends_on is plain start order; restart: unless-stopped stays on the
  plain-Compose files (Swarm ignores it), and the dev app gains it.

The orchestrator used to be what retried a container that started before
Postgres was ready. That is now the app's job: alembic/env.py calls
services/db_ready.wait_for_database before migrating. It retries refused
connections, unresolved hosts, connect timeouts and "the database system
is starting up" with 1-2-4-...-10s spacing for up to 300s, then exits
non-zero; a wrong password or missing database fails at once.
Per-request recovery is the engine's pool_pre_ping.

Also fixes the dev compose database image: postgres:16-alpine has no
vector extension, so migrations could not run against it. It now uses
pgvector/pgvector:pg17 like the other two files.

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

docker-compose.yml

@@ -4,8 +4,8 @@ services:
     ports:
       - "5000:5000"
     depends_on:
-      db:
-        condition: service_healthy
+      - db
+    restart: unless-stopped
     volumes:
       - app_data:/data
       # Or a bind mount, for direct host access to the app's data:
@@ -15,15 +15,10 @@ services:
       SECRET_KEY: "${SECRET_KEY:-dev-secret-change-me}"
       # Optional: a SearXNG instance to list as the web-search backend in Integrations.
       # SEARXNG_URL: "http://searxng:8080"
-    healthcheck:
-      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:5000/api/health')"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-      start_period: 30s
 
   db:
-    image: postgres:16-alpine
+    # Postgres 17 with the vector extension Scribe needs.
+    image: pgvector/pgvector:pg17
     stop_grace_period: 120s
     restart: unless-stopped
     volumes:
@@ -32,14 +27,6 @@ services:
       POSTGRES_USER: ${POSTGRES_USER:-scribe}
       POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-scribe}
       POSTGRES_DB: ${POSTGRES_DB:-scribe}
-    # Lenient on purpose: health only orders app startup, so a stalled check
-    # must not get the database killed.
-    healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-scribe}"]
-      interval: 30s
-      timeout: 10s
-      retries: 10
-      start_period: 180s
 
 volumes:
   pgdata: