refactor(main): IPC 채널 SSOT 일원화 + AppConfig 타입 강화 (WS2)

- ipc-channels.ts SSOT에 9개 그룹/키 추가: INSTRUCTION, SYSTEM_AUDIO,
  POPUP_RESULT/HISTORY/COMMAND/CAPTION, VOICE_PARTIAL, CLIPBOARD, APP,
  VOICE_CONVERSATION.FINISH_LISTENING
- WindowManager/handlers/bootstrap 하드코딩 채널 -> IPC_CHANNELS 교체.
  불일치 4건(result:* vs window:tip*)은 preload 재검증 후 SSOT로 통일.
  notifyRenderer channel: string -> IPCChannel 타입 좁힘.
- AppConfig에 7개 누락 키 추가(customInstructions, llmChains,
  voiceCommandRules, voiceCommandsEnabled, activeInstructionId,
  activeChainId, captionAudioSource) -> as never 16건 제거.
- ChainService/CustomInstructionService/WindowManager dynamic require -> static import.
- services/index.ts 데드 레지스트리 제거 (import 0건).
SKIP: ipcSuccess/ipcError 헬퍼 통일, catch 패턴(별도)
정책: docs/REFACTOR_POLICY.md DP2, DP9

apps/desktop/src/main/services/ChainService.ts

@@ -3,7 +3,7 @@
 // LLMChain을 electron-store에 저장하고, 체인을 순차 실행한다.
 
 import { getLogger } from './LoggerService'
-import { configGet } from './ConfigService'
+import { configGet, configSet } from './ConfigService'
 import { getCustomInstructionService } from './CustomInstructionService'
 import { getLocalLLMService } from './LocalLLMService'
 import { getMainWindow } from '../windows/WindowManager'
@@ -29,7 +29,7 @@ let initialized = false
 
 function loadChains(): LLMChain[] {
   try {
-    const stored = configGet('llmChains' as never) as LLMChain[] | undefined
+    const stored = configGet('llmChains') as LLMChain[] | undefined
     if (Array.isArray(stored) && stored.length > 0) {
       return stored
     }
@@ -41,11 +41,7 @@ function loadChains(): LLMChain[] {
 
 function saveChains(): void {
   try {
-    // eslint-disable-next-line @typescript-eslint/no-require-imports
-    const { configSet } = require('./ConfigService') as {
-      configSet: (key: never, value: never) => void
-    }
-    configSet('llmChains' as never, chains as never)
+    configSet('llmChains', chains)
   } catch (error) {
     logger.warn(
       `Failed to save chains: ${error instanceof Error ? error.message : String(error)}`