chore(17-01): add MinIO to Docker Compose and S3 env config

- Add MinIO + mc init container to docker-compose.dev.yml (fixed creds, console on :9001)
- Add MinIO + mc init container to docker-compose.yml (env var creds, no console)
- Add S3 env vars to app service in production compose
- Remove uploads volume from production compose (replaced by MinIO)
- Add S3 configuration section to .env.example

.env.example

@@ -0,0 +1,23 @@
+# PostgreSQL
+POSTGRES_PASSWORD=changeme
+
+# Logto OIDC (get from Logto Admin Console at http://localhost:3002)
+LOGTO_ENDPOINT=http://localhost:3001
+LOGTO_ADMIN_ENDPOINT=http://localhost:3002
+LOGTO_CLIENT_ID=your-app-client-id
+LOGTO_CLIENT_SECRET=your-app-client-secret
+OIDC_AUTH_SECRET=generate-a-random-32-char-string-here
+
+# Derived (set in docker-compose.yml, not needed here):
+# OIDC_ISSUER=${LOGTO_ENDPOINT}/oidc
+
+# GearBox
+GEARBOX_URL=http://localhost:3000
+
+# S3-compatible Object Storage (MinIO)
+S3_ENDPOINT=http://localhost:9000
+S3_ACCESS_KEY=minioadmin
+S3_SECRET_KEY=minioadmin
+S3_BUCKET=gearbox-images
+S3_REGION=us-east-1
+# S3_PRESIGN_EXPIRY=3600  # Presigned URL expiry in seconds (default: 1 hour)