Enhance Docker support and configuration

- Updated .env.example to recommend using docker.env and secrets for sensitive data.
- Modified .gitignore to include docker.env and secrets directory.
- Adjusted docker-compose.yml to utilize environment files and updated port mappings.
- Implemented read_env_or_file utility for better environment variable management.
- Refactored portfolio and trades routers to use the new utility for fetching environment variables.
- Added integration and phase 2 test updates for new environment variable handling.
- Created new documentation for Docker operations and secret management.
- Added placeholder files for Docker secrets and configuration.

docker.env.example

@@ -0,0 +1,25 @@
+# Copy to docker.env for Docker Compose usage.
+# Keep raw secrets in ./secrets files instead of this env file.
+
+TWS_USERID=your_ibkr_username
+TWS_PASSWORD_FILE=/run/secrets/tws_password
+TRADING_MODE=paper
+# Optional if you need VNC access:
+# VNC_SERVER_PASSWORD_FILE=/run/secrets/vnc_password
+TWOFA_TIMEOUT_ACTION=restart
+AUTO_RESTART_TIME=11:59 PM
+RELOGIN_AFTER_TWOFA_TIMEOUT=yes
+EXISTING_SESSION_DETECTED_ACTION=primaryoverride
+TIME_ZONE=Europe/Istanbul
+
+WEBHOOK_SECRET_FILE=/run/secrets/webhook_secret
+# Optional UI auth:
+# UI_USERNAME_FILE=/run/secrets/ui_username
+# UI_PASSWORD_FILE=/run/secrets/ui_password
+IBKR_CLIENT_ID=1
+MAX_DAILY_LOSS=500.0
+MAX_POSITIONS=5
+MAX_ORDER_VALUE=10000.0
+TRAEFIK_NETWORK=traefik-public
+TRAEFIK_HOST=ibkr.your-tailnet.ts.net
+TRAEFIK_ENTRYPOINT=websecure