fix(deps): Migrate from google.generativeai to google-genai

- Updates requirements.txt to use the new 'google-genai' package.
- Updates import statements and error messages in helpers.py to use the new library.
- Ensures the gemini_api_key.txt is copied into the Docker container to resolve API key errors.

gtm-architect/Dockerfile

@@ -36,6 +36,7 @@ COPY helpers.py .
 COPY config.py .
 # Use the specific requirements file for this app
 COPY gtm-architect/requirements.txt .
+COPY gemini_api_key.txt .
 COPY gtm_db_manager.py .
 
 # Install Python and Node.js dependencies