Flow delete offers to delete its runs, history included

DELETE /runs?flow= removes every Run row of the flow but left its flow_run
rows, so a deleted flow kept appearing in the history. history=true now
drops those too, and the flow delete dialogs (editor and bulk) send it when
"Also delete its runs" is ticked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

backend/tests/api/routes/test_runs.py

@@ -33,7 +33,7 @@ from fluksio.flow.runs import (
 )
 from fluksio.flow.schemas import FlowDef, FlowInput, NodeDef
 from fluksio.flow.store import FlowStore
-from fluksio.models import Run, RunArtifact, RunMetric, RunNode
+from fluksio.models import FlowRun, Run, RunArtifact, RunMetric, RunNode
 
 
 def test_a_run_cache_finds_what_an_earlier_run_recorded(tmp_path):
@@ -1041,6 +1041,33 @@ def test_deleting_a_flows_runs_clears_that_flow_only(client, superuser_token_hea
         session.commit()
 
 
+def test_history_also_clears_a_flows_cascades(client, superuser_token_headers):
+    """What deleting a flow together with its runs asks for."""
+    made = datetime.now(UTC)
+    url = f"{settings.API_V1_STR}/runs"
+    with Session(db_engine) as session:
+        session.add(Run(id="hist-1", flow="gone", status="ok", created_at=made))
+        session.add(FlowRun(id="hist-1", flow="gone", source="run", started_at=made))
+        session.add(FlowRun(id="hist-2", flow="gone", started_at=made))
+        session.add(FlowRun(id="hist-3", flow="other", started_at=made))
+        session.commit()
+
+    plain = client.delete(url, params={"flow": "gone"}, headers=superuser_token_headers)
+    assert plain.status_code == 200
+    with Session(db_engine) as session:
+        assert session.get(FlowRun, "hist-2") is not None
+
+    answer = client.delete(
+        url, params={"flow": "gone", "history": True}, headers=superuser_token_headers
+    )
+    assert answer.status_code == 200
+    with Session(db_engine) as session:
+        left = session.exec(select(FlowRun).where(col(FlowRun.flow) == "gone")).all()
+        assert left == []
+        session.delete(session.get(FlowRun, "hist-3"))
+        session.commit()
+
+
 # -----------------------------------------------------------------------------
 # A cached node's curve
 #