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.

docker-compose.prod.yml

@@ -0,0 +1,15 @@
+services:
+  postgres:
+    ports: []
+
+  redis:
+    ports: []
+
+  minio:
+    ports: []
+
+  mailpit:
+    ports: []
+
+  backend:
+    ports: []