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>

app/games.py

@@ -1,9 +1,12 @@
 import logging
 import sqlite3
-from datetime import datetime, timedelta
+from datetime import datetime, timezone
+from zoneinfo import ZoneInfo
 
 from app.config import DB_PATH
 
+EASTERN = ZoneInfo("America/New_York")
+
 logger = logging.getLogger(__name__)
 
 
@@ -226,6 +229,5 @@ def get_team_standings(team_name):
 
 def utc_to_eastern(utc_time):
     utc_datetime = datetime.strptime(utc_time, "%Y-%m-%dT%H:%M:%SZ")
-    est_offset = timedelta(hours=-4)
-    est_datetime = utc_datetime + est_offset
-    return est_datetime.strftime("%I:%M %p")
+    eastern_datetime = utc_datetime.replace(tzinfo=timezone.utc).astimezone(EASTERN)
+    return eastern_datetime.strftime("%I:%M %p")