fix(ci): increase wait and timeout in migration UI test_01_open_flow

3s wait was too short for the nightly flow editor to render in CI.
Aligned with other tests (5s) and extended expect timeout to 20s.
Also fixes .first -> .first() (Playwright Python method call syntax).

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

Author: lice-reis

tests/github-workflows/migration/test_ui_migration.py

@@ -55,11 +55,11 @@ def _save_results(self):
     def test_01_open_flow(self):
         """Navigate to the migrated flow in the editor."""
         self.page.goto(f"{self.base_url}/flow/{self.flow_id}", wait_until="networkidle")
-        self.page.wait_for_timeout(3000)
+        self.page.wait_for_timeout(5000)
 
         # Verify the flow editor loaded (look for the canvas/reactflow area)
         canvas = self.page.locator(".react-flow, [data-testid='rf__wrapper']")
-        expect(canvas.first).to_be_visible(timeout=15_000)
+        expect(canvas.first()).to_be_visible(timeout=20_000)
 
         self.results["steps"]["open_flow"] = {"status": "pass"}
         self._save_results()