feat(V2-1a): Monorepo 구조 전환 — apps/desktop으로 V1 이동

- npm workspaces 루트 (apps/*, packages/*) 세팅
- V1 전체를 apps/desktop/으로 git mv (src, resources, tests, sidecar,
  scripts, electron.vite.config.ts, electron-builder.yml, vitest.config.ts,
  tsconfig.node.json, tsconfig.web.json)
- apps/desktop/package.json 신규 (name=@d3ro/desktop)
- productName: 'd3ro-voice' 명시 — app.getName()을 고정하여 userData 경로
  %APPDATA%\d3ro-voice\ 그대로 유지 (기존 DB/설정 연속성 보장)
- 루트 package.json을 workspace 루트로 재구성, 공통 devDep만 유지
  (typescript, eslint, prettier)
- turbo.json, tsconfig.base.json 추가 (Turborepo 자체 설치는 별도 sub-phase)
- memory/project_status.md 생성 (규칙 13)

검증:
- npm run typecheck 통과
- npm run build 통과 (electron-vite main+preload+renderer)
- npm run dev 실제 실행 → DB/핫키/Ollama 자동 실행 모두 정상

apps/desktop/tests/shared/errors.test.ts

@@ -0,0 +1,75 @@
+// tests/shared/errors.test.ts
+// D3ROError + IPCResult 헬퍼 테스트
+
+import { describe, it, expect } from 'vitest'
+import { D3ROError, ErrorCode, ipcSuccess, ipcError } from '../../src/shared/errors'
+
+describe('D3ROError', () => {
+  it('code, message, details를 올바르게 설정한다', () => {
+    const err = new D3ROError(ErrorCode.STTModelNotFound, 'Model not found', { modelId: 'large' })
+
+    expect(err.code).toBe(ErrorCode.STTModelNotFound)
+    expect(err.message).toBe('Model not found')
+    expect(err.details).toEqual({ modelId: 'large' })
+    expect(err.name).toBe('D3ROError')
+    expect(err instanceof Error).toBe(true)
+  })
+
+  it('toJSON으로 직렬화할 수 있다', () => {
+    const err = new D3ROError(ErrorCode.LLMServerUnreachable, 'Server down')
+    const json = err.toJSON()
+
+    expect(json.code).toBe(300)
+    expect(json.message).toBe('Server down')
+    expect(json.details).toBeUndefined()
+  })
+
+  it('fromJSON으로 역직렬화할 수 있다', () => {
+    const json = { code: ErrorCode.AudioDeviceNotFound, message: 'No mic' }
+    const err = D3ROError.fromJSON(json)
+
+    expect(err).toBeInstanceOf(D3ROError)
+    expect(err.code).toBe(ErrorCode.AudioDeviceNotFound)
+    expect(err.message).toBe('No mic')
+  })
+})
+
+describe('IPCResult helpers', () => {
+  it('ipcSuccess는 success: true + data를 반환한다', () => {
+    const result = ipcSuccess({ value: 42 })
+
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data).toEqual({ value: 42 })
+    }
+  })
+
+  it('ipcError는 success: false + error를 반환한다', () => {
+    const result = ipcError(ErrorCode.DBQueryFailed, 'Query failed', { table: 'history' })
+
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(result.error.code).toBe(ErrorCode.DBQueryFailed)
+      expect(result.error.message).toBe('Query failed')
+      expect(result.error.details).toEqual({ table: 'history' })
+    }
+  })
+})
+
+describe('ErrorCode', () => {
+  it('에러 코드 범위가 올바르다', () => {
+    // STT: 100-199
+    expect(ErrorCode.STTEngineNotInstalled).toBe(100)
+    expect(ErrorCode.STTGPUNotAvailable).toBe(140)
+
+    // LLM: 300-399
+    expect(ErrorCode.LLMServerUnreachable).toBe(300)
+    expect(ErrorCode.LLMPromptTooLong).toBe(331)
+
+    // Audio: 400-499
+    expect(ErrorCode.AudioDeviceNotFound).toBe(400)
+
+    // System: 900-999
+    expect(ErrorCode.UnknownError).toBe(999)
+  })
+})