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/vite.config.ts

@@ -5,6 +5,7 @@ import react from '@vitejs/plugin-react';
 export default defineConfig(({ mode }) => {
     const env = loadEnv(mode, '.', '');
     return {
+      base: '/b2b/',
       server: {
         port: 3000,
         host: '0.0.0.0',