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.

services/route_calculator.py

@@ -0,0 +1,71 @@
+"""Route calculator service - calculates transit routes using Google Maps API."""
+from models.listing import DestinationMode, Route, RouteLegStep
+from repositories.listing_repository import ListingRepository
+from tqdm.asyncio import tqdm
+from rec import routing
+from models import Listing
+
+
+def _parse_duration(duration_str: str) -> int:
+    """Parse a duration string like '123s' to integer seconds."""
+    return int(duration_str.rstrip("s"))
+
+
+async def calculate_route(
+    repository: ListingRepository,
+    destination_address: str,
+    travel_mode: routing.TravelMode,
+    limit: int | None = None,
+) -> None:
+    """Calculate transit routes for listings to a destination."""
+    listings = await repository.get_listings()
+
+    if limit is not None:
+        listings = listings[:limit]
+
+    destination_mode = DestinationMode(destination_address, travel_mode)
+    updated_listings = await tqdm.gather(
+        *[update_routing_info(listing, destination_mode) for listing in listings],
+        total=len(listings),
+        desc="Updating routing info",
+    )
+    await repository.upsert_listings(
+        [listing for listing in updated_listings if listing is not None]
+    )
+
+
+async def update_routing_info(
+    listing: Listing, destination_mode: DestinationMode
+) -> Listing | None:
+    """Update routing information for a single listing."""
+    if listing.routing_info.get(destination_mode) is not None:
+        # already calculated, do not recompute to save API calls
+        return None
+
+    routes_data = routing.transit_route(
+        listing.latitude,
+        listing.longitude,
+        destination_mode.destination_address,
+        destination_mode.travel_mode,
+    )
+
+    routes: list[Route] = []
+    for route_data in routes_data["routes"]:
+        duration_s = _parse_duration(route_data["duration"])
+        route = Route(
+            legs=[
+                RouteLegStep(
+                    distance_meters=step_data["distanceMeters"],
+                    duration_s=_parse_duration(step_data["staticDuration"]),
+                    travel_mode=routing.TravelMode(step_data["travelMode"]),
+                )
+                for step_data in route_data["legs"][0]["steps"]
+            ],
+            distance_meters=route_data["distanceMeters"],
+            duration_s=duration_s,
+        )
+        routes.append(route)
+    listing.routing_info_json = listing.serialize_routing_info(
+        {**listing.routing_info, **{destination_mode: routes}}
+    )
+    return listing