refactor(config): Switch to environment variables for API keys

- Modifies docker-compose.yml to use  for injecting the Gemini API key, which is more robust than volume mounting.
- Updates helpers.py to prioritize reading the API key from the  environment variable.
- Removes the now-redundant file-based key loading logic from config.py and the Dockerfile.
- This change completely bypasses the problematic file system interactions within the container, providing a definitive fix for the 'API Key missing' error.

docker-compose.yml

@@ -101,10 +101,8 @@ services:
       - ./gtm_db_manager.py:/app/gtm_db_manager.py
       - ./gtm_projects.db:/app/gtm_projects.db
       - ./Log_from_docker:/app/Log_from_docker
-      # Mount API keys
-      - ./gemini_api_key.txt:/app/gemini_api_key.txt
-      - ./gemini_api_key.txt:/app/api_key.txt
-      - ./serpapikey.txt:/app/serpapikey.txt
-    environment:
+      environment:
       - PYTHONUNBUFFERED=1
-      - DB_PATH=/app/gtm_projects.db
+      - DB_PATH=/app/gtm_projects.db
+    env_file:
+      - ./gemini_api_key.txt