Refactor codebase following Clean Code principles and add 229 tests

- Extract helpers to reduce function sizes (listing_tasks, app.py, query.py, listing_fetcher)
  - Replace nonlocal mutations with _PipelineState dataclass in listing_tasks
  - Fix bugs: isinstance→equality check in repository, verify_exp for OIDC tokens
  - Consolidate duplicate filter methods in listing_repository
  - Move hardcoded config to env vars with backward-compatible defaults
  - Simplify CLI decorator to auto-build QueryParameters
  - Add deprecation docstring to data_access.py
  - Test count: 158 → 387 (all passing)

crawler/rec/exceptions.py

@@ -72,3 +72,14 @@ class CircuitBreakerOpenError(RightmoveAPIError):
     """
 
     pass
+
+
+class RoutingApiError(Exception):
+    """Error from the Google Routes API."""
+
+    def __init__(self, status_code: int, response_body: dict):
+        self.status_code = status_code
+        self.response_body = response_body
+        super().__init__(
+            f"Routes API returned status {status_code}: {response_body}"
+        )