fix: stabilize test suite and repair frontend/backend wiring

- meshcore pin >=2.3.0 (EventType.STATS_CORE floor); setup.sh derives
  optional packages from requirements.txt; Python 3.10 warning
- agent-mode wifi clients proxy route + bare-array response handling
- remove dead AIS/ACARS/VDL2 SPA wiring and orphaned partials/CSS
- agent TLE download to data/tle/ (was littering repo root as gp.php)
- gate deferred background init off under pytest (mock-pollution race)
- complete Popen mocks (context manager protocol, communicate tuples)
- real pipe fds in weather-sat decoder tests (fd 10/11 collision caused
  10s SQLite stalls); satellite tests no longer rewrite data/satellites.py
- register 'live' pytest marker, excluded by default
- update stale test assertions to current APIs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_meshcore_routes.py

@@ -25,7 +25,7 @@ def client(app):
 @pytest.fixture(autouse=True)
 def mock_meshcore_client():
     mc = MagicMock()
-    mc.get_state.return_value = MagicMock(value="disconnected")
+    mc.get_state.return_value = (MagicMock(value="disconnected"), None)
     mc.get_messages.return_value = []
     mc.get_nodes.return_value = []
     mc.get_repeaters.return_value = []