feat: RDG session flap rule, qwinsta/logoff queue and dashboard UI (0.9.13)

Detect 302→303 within 1–10s, Problem with 30s dedup, rdg_flap flag.
Agent command poll API, admin qwinsta/logoff from Overview. Migration 016.

backend/app/schemas/list_models.py

@@ -55,6 +55,7 @@ class EventSummary(BaseModel):
     title: str
     summary: str
     actor_user: str | None = None
+    rdg_flap: bool = False
 
     model_config = {"from_attributes": True}