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>

pyproject.toml

@@ -160,7 +160,11 @@ exclude = [
 testpaths = ["tests"]
 python_files = ["test_*.py"]
 python_functions = ["test_*"]
-addopts = "-v --tb=short"
+# 'live' tests drive real SDR hardware — run explicitly with: pytest -m live
+addopts = "-v --tb=short -m 'not live'"
+markers = [
+    "live: tests that require real SDR hardware and run live decoders",
+]
 
 [tool.coverage.run]
 source = ["app", "routes", "utils", "data"]