feat: startup environment check + self-heal (v1.3)

- env_check(): verifies daemon/pineapd/UCI/monitors/recon DB, auto-fixes
  fixable issues and re-verifies; forces runtime SSID-pool broadcast off to
  match the UI (kills the 'pool on but UI shows off' gap)
- server.py --env-check CLI; payload.sh runs it verbosely before starting,
  aborts on core failure
- serve() runs the check at every startup (boot + procd respawn)
- /api/health exposes env report + pool_runtime; /api/recon/status exposes
  wlan0_pinned (2.4GHz under-sampling warning); recon page warns when a
  radio0 AP pins wlan0mon
- recon start failures now include the daemon reason in the UI error
- shared stabilization refactor (_stabilize_uci/PINEAPD_SAFE_UCI/_raise_monitors)
- tests: test_env_check.py (18) + health/recon updates

tests/test_recon.py

@@ -224,7 +224,8 @@ class DaemonSockTest(unittest.TestCase):
             type('C', (), {'args': (), 'body': {'scan_time': 30}})())
         self.assertEqual(status, 502)
         self.assertEqual(data['error'], 'native recon scan failed')
-        self.assertEqual(data['detail'], {'error': 'no radio'})
+        self.assertEqual(data['detail'], 'recon/new: no radio')
+        self.assertEqual(data['daemon'], {'error': 'no radio'})
         self.assertFalse(server._recon_scan_state['active'])