feat: multi-format viewer (Text/Hex/JSON/Binary/Gzip/Deflate/Brotli)

- New format.ts: decodeValue + detectFormat using Node.js zlib
- IPC: redis:decodeValue, redis:detectFormat
- StringEditor: format selector dropdown with auto-detect
- Monaco editor shows decoded value, read-only for compressed formats
- Auto-detect: JSON, Gzip (1f 8b), Deflate (78 xx), non-printable → Hex
- i18n keys for all formats (zh-CN + en)

electron/preload/index.d.ts

@@ -109,6 +109,8 @@ export interface ElectronAPI {
     isConnected: (id: string) => Promise<boolean>
     getCommandLog: () => Promise<any[]>
     clearCommandLog: () => Promise<void>
+    decodeValue: (value: string, format: string) => Promise<string>
+    detectFormat: (value: string) => Promise<string>
     subscribe: (id: string, channels: string[], isPattern: boolean) => Promise<{ success: boolean; error?: string }>
     unsubscribe: (id: string) => Promise<void>
     onSubscribeMessage: (callback: (msg: any) => void) => void