feat(phase3): key browser MVP

- useKeyStore (Pinia): scan, tree view, key data cache, db switching
- KeyBrowser: split pane with KeyList + KeyDetail
- KeyList: SCAN pagination, filter, tree toggle, load more
- KeyDetail: type badge, TTL display, delete, type-based editor dispatch
- StringEditor: view/edit with JSON auto-format
- HashEditor: field table, add/edit/delete fields
- StatusView: INFO dashboard with stat cards + section grid
- MainArea: tab host (Status / Keys)
- RedisService: selectDb, dbSize
- Preload: selectDb, dbSize IPC channels
- App.vue updated with MainArea layout

src/main/ipc-handlers.ts

@@ -115,4 +115,10 @@ export function registerIpcHandlers(): void {
   ipcMain.handle('redis:setTTL', async (_e, id: string, key: string, ttl: number) => {
     await redisService.setKeyTTL(id, key, ttl)
   })
+  ipcMain.handle('redis:selectDb', async (_e, id: string, db: number) => {
+    await redisService.selectDb(id, db)
+  })
+  ipcMain.handle('redis:dbSize', async (_e, id: string) => {
+    return redisService.dbSize(id)
+  })
 }

src/main/redis-service.ts

@@ -164,3 +164,15 @@ export async function setKeyTTL(id: string, key: string, ttl: number): Promise<v
     await client.expire(key, ttl)
   }
 }
+
+export async function selectDb(id: string, db: number): Promise<void> {
+  const client = clients.get(id)
+  if (!client) throw new Error(`Client ${id} not found`)
+  await client.select(db)
+}
+
+export async function dbSize(id: string): Promise<number> {
+  const client = clients.get(id)
+  if (!client) throw new Error(`Client ${id} not found`)
+  return client.dbsize() as Promise<number>
+}