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/conftest.py

@@ -7,6 +7,11 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
+# Must be set before importing app: stops the deferred background-init
+# thread, whose subprocess/DB cleanup fires mid-session and races with
+# test mocks (e.g. a patched subprocess.Popen catching its pkill call)
+os.environ.setdefault("INTERCEPT_SKIP_DEFERRED_INIT", "1")
+
 from app import app as flask_app
 from routes import register_blueprints