Move TZ from docker-compose to .env, document in .env.example

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -7,5 +7,8 @@ POSTGRES_DB=umbra
 DATABASE_URL=postgresql+asyncpg://umbra:changeme_in_production@db:5432/umbra
 SECRET_KEY=change-this-to-a-random-secret-key-in-production
 
+# Timezone (applied to backend + db containers via env_file)
+TZ=Australia/Perth
+
 # Integrations
 OPENWEATHERMAP_API_KEY=your-openweathermap-api-key

docker-compose.yaml

@@ -3,8 +3,6 @@ services:
     image: postgres:16-alpine
     restart: unless-stopped
     env_file: .env
-    environment:
-      - TZ=Australia/Perth
     volumes:
       - postgres_data:/var/lib/postgresql/data
     healthcheck:
@@ -19,8 +17,6 @@ services:
     ports:
       - "8000:8000"
     env_file: .env
-    environment:
-      - TZ=Australia/Perth
     depends_on:
       db:
         condition: service_healthy