feat(investigations): add event impact and work-order feedback flows

Add isolated burst and pollution impact evidence, parallel work-order workflows, persisted notifications and graph updates.

Checkpoint current code. Known follow-ups remain for large pollution result previews and graceful geometry failure.

app/services/operational_scada_coverage.py

@@ -7,7 +7,7 @@ from app.domain.domain_errors import require
 
 def require_complete_scada_evidence(task: dict, evidence: list[dict], refs: list[str]) -> None:
     replay = task.get("source", {}).get("replay_context")
-    if task.get("workflow") != "scada_anomaly" and not replay:
+    if task.get("workflow") not in {"scada_anomaly", "water_pollution"} and not replay:
         return
     target = datetime.fromisoformat(
         replay["knowledge_cutoff"] if replay else task["trigger"]["occurred_at"]