[Architect] #218 Real Gemma 4 + flutter_gemma 0.16.5 design spec

- docs/design/218-gemma-real-integration/README.md (Draft) — 12 섹션 + AC 10
- docs/design/218-gemma-real-integration/fn-gemma_llm_service.md (Draft) — load/generateStructured/_appendSchemaInstruction/_collectFunctionCall 4 함수 명세
- 모델: Gemma 4 E2B QAT 모바일 (HF litert-community)
- flutter_gemma 0.16.5 + ModelType.gemma4 native function calling 확인
- 신규 ADR 발행 안 함 (ADR-0003 결정 #3 유지)
- 변경 범위: gemma_llm_service.dart 본문 교체, _kModelUrl/Sha 상수 치환, main.dart 조건부 override, AndroidManifest + ProGuard
- out of scope: #219 F1 / #220 F2 광범위 / #221 AC10 / #222 keystore

Refs #218

docs/README.md

@@ -68,6 +68,7 @@ docs/
 
 - [204-flutter-bootstrap](./design/204-flutter-bootstrap/) — Phase 1 MVP Drift 21 테이블 + 도메인 함수 + UI 4 화면
 - [215-gemma-frame-suggest](./design/215-gemma-frame-suggest/) — Phase 2-A on-device Gemma 4 프레임 자동 생성
+- [218-gemma-real-integration](./design/218-gemma-real-integration/) — OQ-1 실 Gemma 4 E2B + flutter_gemma 0.16.5 통합 (placeholder → 실 구현)
 
 ### ADR (`adr/`)