feat: Phase 4 - MITRE ATT&CK sync and scheduled job (T-018, T-019)

- Add MITRE sync service via TAXII 2.0 with GitHub fallback
- Upsert attack-pattern objects into techniques table (691 techniques)
- Detect name/description changes and flag review_required on re-sync
- Add APScheduler background job running every 24h
- Add POST /system/sync-mitre endpoint (admin only)
- Add GET /system/scheduler-status endpoint (admin only)
- Configure logging for scheduler and sync visibility
- Update README with new endpoints and project structure

backend/app/main.py

@@ -1,3 +1,4 @@
+import logging
 from contextlib import asynccontextmanager
 
 from fastapi import FastAPI
@@ -7,13 +8,24 @@ from app.routers import auth as auth_router
 from app.routers import techniques as techniques_router
 from app.routers import tests as tests_router
 from app.routers import evidence as evidence_router
+from app.routers import system as system_router
 from app.storage import ensure_bucket_exists
+from app.jobs.mitre_sync_job import start_scheduler, scheduler
+
+# ── Logging ───────────────────────────────────────────────────────────────
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s  %(levelname)-8s  %(name)s — %(message)s",
+)
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     """Startup / shutdown logic."""
     ensure_bucket_exists()
+    start_scheduler()
     yield
+    # Graceful shutdown of the background scheduler
+    scheduler.shutdown(wait=False)
 
 
 app = FastAPI(title="Attack Coverage Platform", lifespan=lifespan)
@@ -32,6 +44,7 @@ app.include_router(auth_router.router, prefix="/api/v1")
 app.include_router(techniques_router.router, prefix="/api/v1")
 app.include_router(tests_router.router, prefix="/api/v1")
 app.include_router(evidence_router.router, prefix="/api/v1")
+app.include_router(system_router.router, prefix="/api/v1")
 
 
 @app.get("/health")