gravityzone: add full GravityZone integration module

Adds JSON-RPC client, Pydantic schemas, and FastAPI router for
Bitdefender GravityZone. Endpoints: status, companies, endpoints,
quarantine, and security sweep across all 55 managed client companies.

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

api/routers/gravityzone.py

@@ -193,6 +193,8 @@ def _build_sweep_result(summaries) -> GZSweepResult:
                 last_seen_dt = datetime.fromisoformat(
                     s.last_seen.replace("Z", "+00:00")
                 )
+                if last_seen_dt.tzinfo is None:
+                    last_seen_dt = last_seen_dt.replace(tzinfo=timezone.utc)
                 if last_seen_dt < stale_cutoff:
                     not_seen_recently += 1
             except (ValueError, AttributeError):
@@ -247,5 +249,5 @@ async def sweep_all_clients(
     current_user: dict = Depends(get_current_user),
 ):
     service = get_gravityzone_service()
-    summaries = await service.security_sweep(ACG_COMPANIES_CONTAINER_ID)
+    summaries = await service.security_sweep_all_clients()
     return _build_sweep_result(summaries)