fix: resolve 4 logic bugs found in code review

- utc_to_eastern: use zoneinfo instead of hardcoded EDT offset (-4)
  so start times are correct in both EST and EDT
- standings: fetch before truncate so a failed API call doesn't wipe
  existing standings data
- routes: call parse_games() once per request instead of three times
- scheduler: wrap run_pending() in try/except so an unhandled exception
  doesn't kill the background thread

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

tests/test_games.py

@@ -101,10 +101,16 @@ class TestGetGameOutcome:
 
 
 class TestUtcToEstTime:
-    def test_converts_utc_to_est(self):
+    def test_converts_utc_to_edt(self):
+        # April is EDT (UTC-4): 23:00 UTC → 07:00 PM EDT
         result = utc_to_eastern("2024-04-10T23:00:00Z")
         assert result == "07:00 PM"
 
+    def test_converts_utc_to_est(self):
+        # January is EST (UTC-5): 23:00 UTC → 06:00 PM EST
+        result = utc_to_eastern("2024-01-15T23:00:00Z")
+        assert result == "06:00 PM"
+
 
 class TestParseGames:
     def test_returns_empty_list_for_none(self):