feat(satellite): add 24-hour periodic TLE auto-refresh

TLE data was only refreshed once at startup. After each refresh, a new
24-hour timer is now scheduled in a finally block so it fires even on
refresh failure. threading moved to module-level import.

routes/satellite.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import math
+import threading
 import time
 import urllib.request
 from datetime import datetime, timedelta
@@ -295,9 +296,15 @@ def _start_satellite_tracker():
         time.sleep(1)
 
 
+_TLE_REFRESH_INTERVAL_SECONDS = 24 * 60 * 60  # 24 hours
+
+
 def init_tle_auto_refresh():
     """Initialize TLE auto-refresh. Called by app.py after initialization."""
-    import threading
+    def _schedule_next_tle_refresh(delay: float = _TLE_REFRESH_INTERVAL_SECONDS) -> None:
+        t = threading.Timer(delay, _auto_refresh_tle)
+        t.daemon = True
+        t.start()
 
     def _auto_refresh_tle():
         try:
@@ -307,10 +314,13 @@ def init_tle_auto_refresh():
                 logger.info(f"Auto-refreshed TLE data for: {', '.join(updated)}")
         except Exception as e:
             logger.warning(f"Auto TLE refresh failed: {e}")
+        finally:
+            # Schedule next refresh regardless of success/failure
+            _schedule_next_tle_refresh()
 
-    # Start auto-refresh in background
+    # First refresh 2 seconds after startup, then every 24 hours
     threading.Timer(2.0, _auto_refresh_tle).start()
-    logger.info("TLE auto-refresh scheduled")
+    logger.info("TLE auto-refresh scheduled (24h interval)")
 
     # Start live position tracker thread
     tracker_thread = threading.Thread(

tests/test_satellite.py

@@ -121,6 +121,39 @@ def test_tracker_position_has_no_observer_fields():
         assert required in pos, f"SSE tracker must emit '{required}'"
 
 
+@patch('routes.satellite.refresh_tle_data', return_value=['ISS'])
+@patch('routes.satellite._load_db_satellites_into_cache')
+def test_tle_auto_refresh_schedules_daily_repeat(mock_load_db, mock_refresh):
+    """After the first TLE refresh, a 24-hour follow-up timer must be scheduled."""
+    import threading as real_threading
+
+    scheduled_delays = []
+
+    class CapturingTimer:
+        def __init__(self, delay, fn, *a, **kw):
+            scheduled_delays.append(delay)
+            self._fn = fn
+            self._delay = delay
+
+        def start(self):
+            # Execute the startup timer inline so we can capture the follow-up
+            if self._delay <= 5:
+                self._fn()
+
+    with patch('routes.satellite.threading') as mock_threading:
+        mock_threading.Timer = CapturingTimer
+        mock_threading.Thread = real_threading.Thread
+
+        from routes.satellite import init_tle_auto_refresh
+        init_tle_auto_refresh()
+
+    # First timer: startup delay (≤5s); second timer: 24h repeat (≥86400s)
+    assert any(d <= 5 for d in scheduled_delays), \
+        f"Expected startup delay timer; got delays: {scheduled_delays}"
+    assert any(d >= 86400 for d in scheduled_delays), \
+        f"Expected ~24h repeat timer; got delays: {scheduled_delays}"
+
+
 # Logic Integration Test (Simulating prediction)
 def test_predict_passes_empty_cache(client):
     """Verify that if the satellite is not in cache, no passes are returned."""