Consolidate tools into a secure Docker architecture with landing page

- Implement a central reverse proxy (Nginx) with Basic Auth on port 8090.
- Create a unified landing page (dashboard) to access B2B Assistant and Market Intelligence.
- Update frontends with relative API paths and base paths for subdirectory routing (/b2b/, /market/).
- Optimize Docker builds with .dockerignore and a Python-based image for market-backend.
- Enable code sideloading for Python logic via Docker volumes.
- Fix TypeScript errors in general-market-intelligence regarding ImportMeta.

b2b-marketing-assistant/App.tsx

@@ -8,7 +8,7 @@ import { translations } from './constants';
 import type { AnalysisStep, AnalysisData, InputData } from './types';
 import { generateMarkdown, downloadFile } from './services/export';
 
-const API_BASE_URL = '/api';
+const API_BASE_URL = 'api';
 
 const App: React.FC = () => {
     const [inputData, setInputData] = useState<InputData>({