fix: reload sentiment cycle history after backfill

backfillData() only refreshed system settings after a successful backfill,
leaving state.sentimentHistory/sentimentHistoryKey populated with the stale
pre-backfill cache, so an already-open sentiment cycle page kept showing the
old one-day history.

After a successful backfill, clear both cache fields and, when the sentiment
cycle view is active, force loadSentimentHistory(true) so the history renders
immediately. Add a frontend contract test covering the refresh path.

Co-authored-by: multica-agent <github@multica.ai>

tests/test_frontend_contract.py

@@ -166,6 +166,15 @@ class FrontendContractTests(unittest.TestCase):
         self.assertIn('id="accountDropdown"', self.html)
         self.assertIn('id="settingsButton"', self.html)
 
+    def test_backfill_clears_sentiment_cache_and_reloads_sentiment_view(self):
+        start = self.script.index("async function backfillData")
+        end = self.script.index("async function openAdminSettings", start)
+        backfill = self.script[start:end]
+        self.assertIn("state.sentimentHistory = null;", backfill)
+        self.assertIn('state.sentimentHistoryKey = "";', backfill)
+        self.assertIn('if (state.activeView === "sentimentCycleView")', backfill)
+        self.assertIn("await loadSentimentHistory(true);", backfill)
+
     def test_screener_uses_progressive_strategy_editor(self):
         for step in ("regime", "strategy", "run", "result"):
             self.assertIn(f'data-screener-step="{step}"', self.html)