feat: canonical flow directory with sync engine (files are source of truth)

backend/scripts/make_flow_fixtures.py

@@ -6,6 +6,10 @@ Langflow UI would export. Run with the backend venv (has the `lfx` dev dep)::
 
     uv run python scripts/make_flow_fixtures.py
 
+Writes to two places:
+- backend/tests/fixtures/flows/ (test fixtures, never deployed as-is)
+- backend/flows/ (canonical source of truth, synced into DB + LFX)
+
 Then verify::
 
     uv run lfx validate --level 4 backend/tests/fixtures/flows/
@@ -21,6 +25,7 @@ from pathlib import Path
 
 REPO_ROOT = Path(__file__).resolve().parent.parent.parent
 FIXTURE_DIR = REPO_ROOT / "backend" / "tests" / "fixtures" / "flows"
+FLOW_DIR = REPO_ROOT / "backend" / "flows"
 
 HANDLE_QUOTE = "\u0153"  # ReactFlow handle-id quoting used by Langflow exports
 
@@ -430,14 +435,16 @@ def build_approval_handoff() -> dict:
 
 def main() -> None:
     FIXTURE_DIR.mkdir(parents=True, exist_ok=True)
+    FLOW_DIR.mkdir(parents=True, exist_ok=True)
     flows = {
         "simple_rule.json": build_simple_rule(),
         "approval_handoff.json": build_approval_handoff(),
     }
     for filename, doc in flows.items():
-        path = FIXTURE_DIR / filename
-        path.write_text(json.dumps(doc, indent=2, ensure_ascii=False) + "\n")
-        print(f"wrote {path}")
+        payload = json.dumps(doc, indent=2, ensure_ascii=False) + "\n"
+        for target in (FIXTURE_DIR / filename, FLOW_DIR / filename):
+            target.write_text(payload)
+            print(f"wrote {target}")
 
 
 if __name__ == "__main__":