fix(compose): set an explicit, tunable database connection_limit

The app pins DATABASE_URL in the compose environment block, which shadows
any connection_limit an operator sets in .env, so Prisma fell back to its
default pool (cpu_count*2+1 — 9 on a 4-core host). A combined web+worker
process starves that pool under background AI and rollup load, leaving
HTTP requests waiting on the pool until they time out. Set connection_limit
explicitly (default 20, override via DB_CONNECTION_LIMIT) plus a pool_timeout
override, so the pool can be sized to the host and its database.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -18,7 +18,14 @@ services:
     ports:
       - "3000:3000"
     environment:
-      DATABASE_URL: "postgresql://healthlog:${POSTGRES_PASSWORD}@db:5432/healthlog?schema=public"
+      # connection_limit is set explicitly: Prisma's own default is
+      # cpu_count*2+1, which starves the combined web+worker process
+      # (HEALTHLOG_PROCESS_TYPE=all) under background AI/rollup load. Default
+      # 20 suits a small host; raise DB_CONNECTION_LIMIT on a busy one (keep it
+      # below the database's max_connections, leaving headroom for pg-boss,
+      # migrations, and backups). pool_timeout is the seconds a query waits for
+      # a free connection before erroring.
+      DATABASE_URL: "postgresql://healthlog:${POSTGRES_PASSWORD}@db:5432/healthlog?schema=public&connection_limit=${DB_CONNECTION_LIMIT:-20}&pool_timeout=${DB_POOL_TIMEOUT:-20}"
       NODE_ENV: production
       ENCRYPTION_KEY: "${ENCRYPTION_KEY}"
       ENCRYPTION_KEYS: "${ENCRYPTION_KEYS:-}"