Merge Workstream G: device pairing + ingestion + live broadcast

Resolved conflict in main.py: combined both workstreams' router imports
and registrations (device_router from G, inventory_router from C).
143/143 backend tests pass after cleaning stray pollution from an
earlier parallel workstream run against the shared test DB.

backend/app/main.py

@@ -13,6 +13,7 @@ from app.config import settings
 from app.db import Base, async_session_maker, engine
 from app.routes.auth import router as auth_router
 from app.routes.codex import router as codex_router
+from app.routes.device import router as device_router
 from app.routes.inventory import router as inventory_router
 from app.routes.shop import router as shop_router
 from app.session_cleanup import delete_expired_sessions
@@ -65,6 +66,7 @@ async def lifespan(app: FastAPI):
 app = FastAPI(title="Quantumancy", lifespan=lifespan)
 app.include_router(auth_router)
 app.include_router(codex_router)
+app.include_router(device_router)
 app.include_router(inventory_router)
 app.include_router(shop_router)
 app.include_router(ws_router)