fix(deployment): remove db service from base config - use external PostgreSQL stack for all environments

User specified that all environments (local, staging, production) should
use external PostgreSQL stacks consistently instead of embedded database.

Changes:
- Removed db service definition from base config (lines 87-114)
- Removed db dependency from queue-worker service
- Updated php-test DB_HOST to use external 'postgres' service

This eliminates the need for production overrides and creates uniform
architecture across all environments. The application-db-1 container
will no longer be started, fixing deployment failure.

This is the tenth cumulative fix for production deployment pipeline.

Related commits:
- f97863a: Add image references to production config
- 5b5fdee: Fix registry upload with sequential push
- a1b9a53: Remove CI test file
- 0b54086: Fix Node.js cache dependency
- 6263d7a: Trigger CI workflow verification
- 08f6f64: Stable IMAGE_TAG
- 2e539ed: Add build: null overrides
- 6e1faab: Deploy docker-compose via scp
- c1d6a71: Fix scp working directory
- a4ca6e9: Trigger pipeline
- 0c0c3ba: Fix .env mount conflict
- 41882da: Fix storage/var volume mounts
- 477fe67: Fix Redis health check

docker-compose.base.yml

@@ -76,7 +76,7 @@ services:
     environment:
       APP_ENV: testing
       APP_DEBUG: true
-      DB_HOST: db
+      DB_HOST: postgres  # External PostgreSQL Stack service
       REDIS_HOST: redis
     networks:
       - backend
@@ -84,34 +84,10 @@ services:
     entrypoint: []
     command: ["php", "-v"]
 
-  db:
-    image: postgres:16-alpine
-    environment:
-      POSTGRES_DB: ${DB_DATABASE:-michaelschiemer}
-      POSTGRES_USER: ${DB_USERNAME:-postgres}
-      # SECURITY: POSTGRES_PASSWORD must be set explicitly (no hardcoded fallback)
-      # Set DB_PASSWORD in .env.local for local development
-      # Use Docker Secrets in production/staging via DB_PASSWORD_FILE
-      POSTGRES_PASSWORD: ${DB_PASSWORD}
-      # Performance & Connection Settings
-      POSTGRES_INITDB_ARGS: "-E UTF8 --locale=C"
-      PGDATA: /var/lib/postgresql/data/pgdata
-    volumes:
-      - db_data:/var/lib/postgresql/data
-      - "${DB_CONFIG_PATH:-./docker/postgres/postgresql.conf}:/etc/postgresql/postgresql.conf:ro"
-      - "${DB_INIT_PATH:-./docker/postgres/init}:/docker-entrypoint-initdb.d:ro"
-    command:
-      - "postgres"
-      - "-c"
-      - "config_file=/etc/postgresql/postgresql.conf"
-    healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${DB_USERNAME:-postgres} -d ${DB_DATABASE:-michaelschiemer}"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-      start_period: 30s
-    networks:
-      - backend
+  # Database service removed - all environments use external PostgreSQL Stack
+  # Local: deployment/stacks/postgresql/
+  # Staging: deployment/stacks/postgresql/
+  # Production: deployment/stacks/postgresql/
 
   redis:
     image: redis:7-alpine
@@ -139,8 +115,7 @@ services:
         condition: service_healthy
       redis:
         condition: service_healthy
-      db:
-        condition: service_healthy
+      # Note: PostgreSQL is external service, connection via app-internal network
     volumes:
       # Use same storage volumes as PHP container for consistency
       # Persistent volumes for queue and logs