Flatten repo structure: move crawler/ to root, remove vqa/ and immoweb/

The crawler subdirectory was the only active project. Moving it to the
repo root simplifies paths and removes the unnecessary nesting. The
vqa/ and immoweb/ directories were legacy/unused and have been removed.

Updated .drone.yml, .gitignore, .claude/ docs, and skills to reflect
the new flat structure.

frontend/nginx.conf

@@ -0,0 +1,23 @@
+server {
+    listen 80;
+    server_name _;
+
+    # Root directory for static files (must match Docker COPY path)
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Serve static files
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    # Enable gzip compression
+    gzip on;
+    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;
+
+    # Cache static assets
+    # location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff2)$ {
+    #     expires 1y;
+    #     add_header Cache-Control "public, immutable";
+    # }
+}