fix(wifi): public check_internet_connectivity(); absolute systemctl path; stricter mode assertion

wifi_manager.py:
- Add public check_internet_connectivity() wrapping the private method so the
  daemon does not reach into the private API

wifi_monitor_daemon.py:
- Call wifi_manager.check_internet_connectivity() instead of the private
  _check_internet_connectivity()
- Use /usr/bin/systemctl (absolute path) instead of bare "systemctl"
- Wrap NM restart in try/except with check=True; only reset
  _consecutive_internet_failures on success — on CalledProcessError or other
  exception, log the error and leave the counter unchanged so the next cycle
  retries

test/test_wifi_manager_ap.py:
- Replace loose `assert "ap" in add_calls[0]` (list-membership check that
  could be satisfied by any element equal to "ap") with an explicit key/value
  check: locate "802-11-wireless.mode" in the command list and assert the next
  element is exactly "ap"

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/test_wifi_manager_ap.py

@@ -129,7 +129,15 @@ def test_nmcli_ap_profile_has_no_security_params(manager: WiFiManager) -> None:
     assert "psk" not in add_str, "AP profile must not include a PSK/password"
     assert "wpa" not in add_str.lower(), "AP profile must not reference WPA"
     assert "802-11-wireless.mode" in add_str, "AP profile must declare wireless mode"
-    assert "ap" in add_calls[0], "Wireless mode value must be 'ap'"
+    # Verify the value for 802-11-wireless.mode is exactly "ap" — check the element
+    # that immediately follows the key in the command list, not a loose substring match.
+    cmd = add_calls[0]
+    try:
+        mode_idx = cmd.index("802-11-wireless.mode")
+        assert cmd[mode_idx + 1] == "ap", \
+            f"802-11-wireless.mode value must be exactly 'ap', got {cmd[mode_idx + 1]!r}"
+    except ValueError:
+        pytest.fail("802-11-wireless.mode not found as a list element in nmcli command")
 
 
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