Add bulk import for evolutions, routes, and bosses

Add three new bulk import endpoints that accept the same JSON format as
their corresponding export endpoints, enabling round-trip compatibility:

- POST /evolutions/bulk-import (upsert by from/to pokemon pair)
- POST /games/{id}/routes/bulk-import (reuses seed loader for hierarchy)
- POST /games/{id}/bosses/bulk-import (reuses seed loader with team data)

Generalize BulkImportModal to support all entity types with configurable
title, example, and result labels. Wire up Bulk Import buttons on
AdminEvolutions, and AdminGameDetail routes/bosses tabs.

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

backend/src/app/api/bosses.py

@@ -11,6 +11,8 @@ from app.models.boss_pokemon import BossPokemon
 from app.models.boss_result import BossResult
 from app.models.game import Game
 from app.models.nuzlocke_run import NuzlockeRun
+from app.models.pokemon import Pokemon
+from app.models.route import Route
 from app.schemas.boss import (
     BossBattleCreate,
     BossBattleResponse,
@@ -20,6 +22,8 @@ from app.schemas.boss import (
     BossResultCreate,
     BossResultResponse,
 )
+from app.schemas.pokemon import BulkBossItem, BulkImportResult
+from app.seeds.loader import upsert_bosses
 
 router = APIRouter()
 
@@ -164,6 +168,34 @@ async def delete_boss(
     return Response(status_code=204)
 
 
+@router.post("/games/{game_id}/bosses/bulk-import", response_model=BulkImportResult)
+async def bulk_import_bosses(
+    game_id: int,
+    items: list[BulkBossItem],
+    session: AsyncSession = Depends(get_session),
+):
+    vg_id = await _get_version_group_id(session, game_id)
+
+    # Build pokeapi_id -> id mapping
+    result = await session.execute(select(Pokemon.pokeapi_id, Pokemon.id))
+    dex_to_id = {row.pokeapi_id: row.id for row in result}
+
+    # Build route name -> id mapping for after_route_name resolution
+    result = await session.execute(
+        select(Route.name, Route.id).where(Route.version_group_id == vg_id)
+    )
+    route_name_to_id = {row.name: row.id for row in result}
+
+    bosses_data = [item.model_dump() for item in items]
+    try:
+        count = await upsert_bosses(session, vg_id, bosses_data, dex_to_id, route_name_to_id)
+    except Exception as e:
+        raise HTTPException(status_code=400, detail=f"Failed to import bosses: {e}")
+
+    await session.commit()
+    return BulkImportResult(created=count, updated=0, errors=[])
+
+
 @router.put(
     "/games/{game_id}/bosses/{boss_id}/pokemon",
     response_model=BossBattleResponse,