Phase 6 구현: 커스텀 명령어 + i18n (ko/en)

- CustomInstructionService: 프리셋 5개 (번역/요약/전문리라이트/코드설명/자유프롬프트)
- 커스텀 명령어 CRUD + 프리셋 보호 (삭제 불가)
- CommandsPage: 명령어 목록 + 추가/편집 다이얼로그
- i18n: ko.json/en.json 리소스 파일, t() 함수, React 컨텍스트
- IPC: instruction 핸들러 6개
- AppLayout: Commands 네비게이션 추가

src/main/bootstrap.ts

@@ -8,6 +8,7 @@ import { getVoiceModeService } from './services/VoiceModeService'
 import { getLocalLLMService } from './services/LocalLLMService'
 import { getHistoryService } from './services/HistoryService'
 import { getTextInsertService } from './services/TextInsertService'
+import { getCustomInstructionService } from './services/CustomInstructionService'
 import { initDatabase } from './db'
 import {
   createMainWindow,
@@ -41,6 +42,7 @@ export async function bootstrap(): Promise<void> {
     { name: 'create-windows', critical: true, fn: createWindows },
     { name: 'tray', critical: false, fn: initTray },
     { name: 'ipc-handlers', critical: true, fn: initIpcHandlers },
+    { name: 'custom-instructions', critical: false, fn: initCustomInstructions },
     { name: 'popup-preload', critical: false, fn: initPopupWindows },
     { name: 'hotkey', critical: false, fn: initHotkey },
     { name: 'voice-mode', critical: false, fn: initVoiceMode },
@@ -95,6 +97,10 @@ async function initHotkey(): Promise<void> {
   hotkey.start()
 }
 
+async function initCustomInstructions(): Promise<void> {
+  getCustomInstructionService().initialize()
+}
+
 async function initPopupWindows(): Promise<void> {
   preloadPopupWindows()
   setupHistoryPopupIPC()