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.

rec/route_serializer.py

@@ -0,0 +1,47 @@
+import dataclasses
+import json
+from typing import List
+
+from models.listing import DestinationMode, Route, RouteLegStep
+from rec import routing
+
+
+class RouteSerializer:
+    @staticmethod
+    def serialize(routing_info: dict[DestinationMode, list[Route]]) -> str:
+        return json.dumps(
+            {
+                json.dumps(dataclasses.asdict(destination_mode)): [
+                    json.dumps(dataclasses.asdict(route)) for route in routes
+                ]
+                for destination_mode, routes in routing_info.items()
+            }
+        )
+
+    @staticmethod
+    def deserialize(route_data_json: str) -> dict[DestinationMode, List[Route]]:
+        json_data = json.loads(route_data_json)
+        destination_routes = {}
+        for destination_mode_str, routes_json in json_data.items():
+            parsed_destination = json.loads(destination_mode_str)
+            destination_mode = DestinationMode(
+                destination_address=parsed_destination["destination_address"],
+                travel_mode=routing.TravelMode(parsed_destination["travel_mode"]),
+            )
+            parsed_route = json.loads(routes_json[0])
+            routes = [
+                Route(
+                    legs=[
+                        RouteLegStep(
+                            distance_meters=step["distance_meters"],
+                            duration_s=step["duration_s"],
+                            travel_mode=routing.TravelMode(step["travel_mode"]),
+                        )
+                        for step in parsed_route["legs"]
+                    ],
+                    distance_meters=parsed_route["distance_meters"],
+                    duration_s=int(parsed_route["duration_s"]),
+                )
+            ]
+            destination_routes[destination_mode] = routes
+        return destination_routes