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.

tests/test_phase2.py

@@ -2,6 +2,7 @@
 Phase 2 test suite — uses TestClient with mocked IB and DB dependencies.
 Run: pytest tests/test_phase2.py -v
 """
+import os
 import sqlite3
 import sys
 import threading
@@ -88,7 +89,7 @@ _app.include_router(portfolio.router)
 client = TestClient(_app, raise_server_exceptions=False)
 
 WRONG_SECRET = "wrong_secret"
-RIGHT_SECRET = "your_super_secret_string_123"
+RIGHT_SECRET = os.getenv("WEBHOOK_SECRET", "your_super_secret_string_123")
 
 
 # ── Tests ─────────────────────────────────────────────────────────────────────