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/Caddyfile.dev

@@ -0,0 +1,11 @@
+{$DEV_HOST:localhost}:443 {
+    tls internal
+
+    handle /api/* {
+        reverse_proxy app:5001
+    }
+
+    handle {
+        reverse_proxy frontend:5173
+    }
+}