Add hierarchical route grouping for multi-area locations

Locations like Mt. Moon (with 1F, B1F, B2F floors) are now grouped so
only one encounter can be logged per location group, enforcing Nuzlocke
first-encounter rules correctly.

- Add parent_route_id column with self-referential FK to routes table
- Add parent/children relationships on Route model
- Update games API to return hierarchical route structure
- Add validation in encounters API to prevent parent route encounters
  and duplicate encounters within sibling routes (409 conflict)
- Update frontend with collapsible RouteGroup component
- Auto-derive route groups from PokeAPI location/location-area structure
- Regenerate seed data with 70 parent routes and 315 child routes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/app/seeds/run.py

@@ -66,10 +66,24 @@ async def seed():
                         print(f"  Warning: route '{route['name']}' not found")
                         continue
 
-                    enc_count = await upsert_route_encounters(
-                        session, route_id, route["encounters"], dex_to_id
-                    )
-                    total_encounters += enc_count
+                    # Parent routes may have empty encounters
+                    if route["encounters"]:
+                        enc_count = await upsert_route_encounters(
+                            session, route_id, route["encounters"], dex_to_id
+                        )
+                        total_encounters += enc_count
+
+                    # Handle child routes
+                    for child in route.get("children", []):
+                        child_id = route_map.get(child["name"])
+                        if child_id is None:
+                            print(f"  Warning: child route '{child['name']}' not found")
+                            continue
+
+                        enc_count = await upsert_route_encounters(
+                            session, child_id, child["encounters"], dex_to_id
+                        )
+                        total_encounters += enc_count
 
                 print(f"  {game_slug}: {len(route_map)} routes")