Fix TypeScript errors in frontend build

Cast boss type select value to union type and remove unused
AdvanceLegInput import.

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

frontend/src/hooks/useGenlockes.ts

@@ -1,6 +1,6 @@
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { advanceLeg, createGenlocke, getGamesByRegion, getGenlockes, getGenlocke, getGenlockeGraveyard, getGenlockeLineages, getLegSurvivors } from '../api/genlockes'
-import type { AdvanceLegInput, CreateGenlockeInput } from '../types/game'
+import type { CreateGenlockeInput } from '../types/game'
 
 export function useGenlockes() {
   return useQuery({