Parameterize docker-compose for server deployment

Compose settings:

- Reworked docker-compose.yml to use environment-variable driven configuration.

- Added shared app env anchors for backend and worker to reduce duplication.

- Made ports, credentials, security limits, SMTP, and storage options configurable.

Production profile:

- Added docker-compose.prod.yml override to close internal service ports.

- Keeps external attack surface minimal for Linux server deployments.

Docs and ops:

- Added .env.docker.example with full variable set for server setup.

- Updated README with quick-start and production launch commands.

README.md

@@ -35,9 +35,17 @@ celery -A app.celery_app:celery_app worker --loglevel=info
 
 Run full stack (web + api + worker + postgres + redis + minio + mailpit):
 
-1. docker compose up --build
+1. cp .env.docker.example .env
+2. edit `.env` (`SECRET_KEY`, passwords, domain)
+3. docker compose up -d --build
 2. Open:
    - Web: http://localhost
    - API docs: http://localhost:8000/docs
    - Mailpit UI: http://localhost:8025
    - MinIO console: http://localhost:9001
+
+### Production Mode
+
+Use production override to close internal ports (postgres/redis/minio/mailpit/backend):
+
+docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d --build