Add version groups to share routes and boss battles across games

Routes and boss battles now belong to a version_group instead of
individual games, so paired versions (e.g. Red/Blue, Gold/Silver)
share the same route structure and boss battles. Route encounters
gain a game_id column to support game-specific encounter tables
within a shared route. Includes migration, updated seeds, API
changes, and frontend type updates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.beans/nuzlocke-tracker-lab1--add-version-groups-table-share-routes-boss-battles.md

@@ -0,0 +1,20 @@
+---
+# nuzlocke-tracker-lab1
+title: Add version_groups table, share routes & boss battles across version groups
+status: completed
+type: feature
+priority: normal
+created_at: 2026-02-08T10:39:00Z
+updated_at: 2026-02-08T10:46:43Z
+---
+
+Introduce version_groups table and re-parent routes and boss_battles from game_id to version_group_id. Add game_id to route_encounters for per-game encounter data.
+
+## Checklist
+- [x] Phase 1: Backend models (VersionGroup, Game, Route, RouteEncounter, BossBattle)
+- [x] Phase 2: Alembic migration
+- [x] Phase 3: Backend schemas
+- [x] Phase 4: Backend API updates
+- [x] Phase 5: Seed loader updates
+- [x] Phase 6: Frontend type/API/hook updates
+- [x] Verification: migration runs, TypeScript compiles