feat: DEVONthink 제거 + 모닝 브리핑 추가

- DEVONthink 의존성 제거 → kb_writer 전환 (news_digest, inbox_processor, mail pipeline)
- devonthink_bridge.py, plist 삭제
- morning_briefing.py 신규 (매일 07:30, 일정·메일·보고·뉴스 → Synology Chat)
- intent_service.py 분류기 프롬프트 개선 + 키워드 fallback
- migrate-v5.sql (news_digest_log kb_path 컬럼)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -56,9 +56,6 @@ IMAP_USER=hyungi
 IMAP_PASSWORD=changeme
 IMAP_SSL=true
 
-# DEVONthink (devonthink_bridge.py — 지식 저장소)
-DEVONTHINK_APP_NAME=DEVONthink
-
 # Karakeep (NAS Docker — 북마크/뉴스 저장)
 KARAKEEP_URL=http://192.168.1.227:3000
 KARAKEEP_API_KEY=changeme
@@ -70,7 +67,6 @@ API_MONTHLY_LIMIT=10.00
 HEIC_CONVERTER_URL=http://host.docker.internal:8090
 CHAT_BRIDGE_URL=http://host.docker.internal:8091
 CALDAV_BRIDGE_URL=http://host.docker.internal:8092
-DEVONTHINK_BRIDGE_URL=http://host.docker.internal:8093
 MAIL_BRIDGE_URL=http://host.docker.internal:8094
 KB_WRITER_URL=http://host.docker.internal:8095
 NOTE_BRIDGE_URL=http://host.docker.internal:8098