chore(deps): 미사용 의존성 8종 제거 + electron-builder Linux 섹션 삭제 (WS-DEPS)

- apps/desktop/package.json에서 8종 제거(각 역추적 0건):
  @mui/icons-material, @d3ro/api-client, fluent-ffmpeg, @types/fluent-ffmpeg,
  pdf-parse, node-record-lpcm16, electron-audio-loopback, @electron-toolkit/preload
- node-record-lpcm16.d.ts 타입 선언 삭제
- electron-builder.yml Linux 섹션 삭제 (CI는 win/mac만 호출)
참고: @mui/icons-material은 @d3ro/ui 트랜시티브로 잔존(desktop 직접 의존에서는 제거)
정책: docs/REFACTOR_POLICY.md DP9

apps/desktop/src/main/types/node-record-lpcm16.d.ts

@@ -1,33 +0,0 @@
-// Type declarations for node-record-lpcm16 (no @types package available)
-
-declare module 'node-record-lpcm16' {
-  import { ChildProcess } from 'child_process'
-  import { Readable } from 'stream'
-
-  interface RecordingOptions {
-    sampleRate?: number
-    channels?: number
-    compress?: boolean
-    threshold?: number
-    thresholdStart?: number | null
-    thresholdEnd?: number | null
-    silence?: string
-    recorder?: 'sox' | 'rec' | 'arecord'
-    endOnSilence?: boolean
-    audioType?: string
-    device?: string
-  }
-
-  interface Recording {
-    process: ChildProcess
-    stop(): void
-    pause(): void
-    resume(): void
-    isPaused(): boolean
-    stream(): Readable
-  }
-
-  function record(options?: RecordingOptions): Recording
-
-  export { record, Recording, RecordingOptions }
-}