feat(phase4e): batch delete with multi-select

- KeyList: multi-select mode with checkbox toggle
- Batch delete bar shows selected count + delete button
- RedisService: batchDelete using pipeline
- Preload: batchDelete IPC channel

src/main/ipc-handlers.ts

@@ -179,4 +179,7 @@ export function registerIpcHandlers(): void {
   ipcMain.handle('redis:memoryUsage', async (_e, id: string, key: string) => {
     return redisService.memoryUsage(id, key)
   })
+  ipcMain.handle('redis:batchDelete', async (_e, id: string, keys: string[]) => {
+    return redisService.batchDelete(id, keys)
+  })
 }

src/main/redis-service.ts

@@ -278,3 +278,15 @@ export async function memoryUsage(id: string, key: string): Promise<number | nul
   if (!client) throw new Error(`Client ${id} not found`)
   return client.memory('USAGE', key) as Promise<number | null>
 }
+
+export async function batchDelete(id: string, keys: string[]): Promise<number> {
+  const client = clients.get(id)
+  if (!client) throw new Error(`Client ${id} not found`)
+  if (keys.length === 0) return 0
+  const pipeline = client.pipeline()
+  for (const key of keys) {
+    pipeline.del(key)
+  }
+  const results = await pipeline.exec()
+  return results?.filter(([err]) => !err).length ?? 0
+}