feat: barre d'apps commune et références croisées des notes (#215)

backend/main.py

@@ -522,6 +522,7 @@ from backend.routers.config import _load_config
 from backend.routers.config import router as config_router
 from backend.routers.conflicts import router as conflicts_router
 from backend.routers.duplicates import router as duplicates_router
+from backend.routers.external_refs import router as external_refs_router
 from backend.routers.file_chat import router as file_chat_router
 from backend.routers.files_media import router as files_media_router
 from backend.routers.files_read import router as files_read_router
@@ -543,6 +544,7 @@ app.include_router(bookslm_router)
 app.include_router(skills_router)
 app.include_router(health_router)  # ROADMAP #85 T1 — System / health
 app.include_router(history_router)  # ROADMAP #85 T8 — History
+app.include_router(external_refs_router)  # Fusion #215 — Références croisées (ACC-1.3)
 app.include_router(realtime_router)  # ROADMAP #85 T9 — SSE + collab WS
 app.include_router(search_router)  # ROADMAP #85 T5 — Search
 app.include_router(backups_router)  # ROADMAP #85 T4 — Backups