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>

app.py

@@ -1293,6 +1293,11 @@ def _init_app() -> None:
         except Exception as e:
             logger.warning(f"Ground station scheduler init failed: {e}")
 
+    # Skip background init when disabled (set by tests — the deferred thread
+    # fires mid-session and its subprocess/DB cleanup races with test mocks)
+    if os.environ.get("INTERCEPT_SKIP_DEFERRED_INIT") == "1":
+        return
+
     threading.Thread(target=_deferred_init, daemon=True).start()