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>

frontend/src/types/game.ts

@@ -13,6 +13,11 @@ export interface Route {
   name: string
   gameId: number
   order: number
+  parentRouteId: number | null
+}
+
+export interface RouteWithChildren extends Route {
+  children: Route[]
 }
 
 export interface Pokemon {