Add system diagnostics, power controls, and WiFi radio toggle to Tools tab (#389)

* Add system diagnostics, power controls, and WiFi radio toggle to Tools tab

Expands the web UI Tools tab with safe, purpose-built controls so users can
manage the Pi without SSHing in, instead of an arbitrary-command terminal
(the web UI has no auth and CSRF is disabled, so a shell would be unsafe).

- System Diagnostics card: renders the existing but previously-unused
  GET /api/v3/system/status endpoint (CPU, memory, temp, disk, uptime),
  with a manual refresh and a 10s poll.
- System Power section: reboot/shutdown buttons wired to the existing
  reboot_system / shutdown_system actions, behind a confirm step, with a
  dedicated powerAction() helper that treats the dropped connection as the
  expected "going offline" outcome rather than an error.
- Network Radio section: WiFi on/off toggle backed by new
  GET/POST /api/v3/wifi/radio endpoints and WiFiManager.set_wifi_radio() /
  get_wifi_radio_state(). Disabling WiFi is refused unless a wired
  connection is present (reusing the existing lockout guards), with an
  explicit force-off confirmation for advanced users.

No new privileged commands: uses nmcli radio wifi on|off (already
sudo-allowlisted) and the existing reboot/poweroff grants, so the
sudoers-alignment guard test stays green. Bluetooth toggle intentionally
omitted since the installer removes the BlueZ stack for LED timing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019X3he87Ggr1qt8y7mnFeuE

* Harden WiFi radio endpoint and diagnostics poll (review feedback)

Addresses code review feedback on the Tools tab additions:

- api_v3.py: parse the `enabled` POST field with the same string-aware
  coercion as `force`. A plain bool() cast turned {"enabled":"false"} into
  True (enabling instead of disabling) for any non-UI API caller.
- wifi_manager.set_wifi_radio() now returns a reason code alongside
  (success, message); the /wifi/radio error response includes it. The Tools
  UI only shows the force-off confirmation when reason == 'no_ethernet', so a
  genuine nmcli failure surfaces its real error instead of a misleading
  "no wired connection" prompt that would just retry into the same failure.
- tools.html: gate the 10s diagnostics poll on panel visibility
  (document.hidden / offsetParent), so switching to another tab stops the
  recurring /api/v3/system/status calls instead of churning the Pi off-screen.
  The initial load and manual Refresh remain unconditional.

Verified: {"enabled":"false"} now disables (refused w/ reason:no_ethernet),
{"enabled":"true"} enables; inline JS passes node --check; py_compile clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019X3he87Ggr1qt8y7mnFeuE

* Narrow WiFi-disable fallback except and add stack trace (review)

Addresses a CodeRabbit nitpick: the fallback handler in set_wifi_radio()'s
disable path caught bare Exception and logged without a traceback. Narrow it to
(OSError, subprocess.SubprocessError) — the errors subprocess.run realistically
raises — and log with exc_info=True for full context on the Pi. Anything
genuinely unexpected now propagates to the endpoint's outer handler (500),
matching the codebase's specific-exception convention.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019X3he87Ggr1qt8y7mnFeuE

---------

Co-authored-by: Claude <noreply@anthropic.com>

web_interface/blueprints/api_v3.py

@@ -7252,6 +7252,74 @@ def set_auto_enable_ap_mode():
             'message': 'An error occurred; see logs for details'
         }), 500
 
+@api_v3.route('/wifi/radio', methods=['GET'])
+def get_wifi_radio():
+    """Get current WiFi radio state (enabled/disabled) and wired-fallback status."""
+    try:
+        from src.wifi_manager import WiFiManager
+
+        wifi_manager = WiFiManager()
+        state = wifi_manager.get_wifi_radio_state()
+
+        return jsonify({
+            'status': 'success',
+            'data': state
+        })
+    except Exception as e:
+        logger.error("Error getting WiFi radio state", exc_info=True)
+        return jsonify({
+            'status': 'error',
+            'message': 'An error occurred; see logs for details'
+        }), 500
+
+@api_v3.route('/wifi/radio', methods=['POST'])
+def set_wifi_radio():
+    """Turn the WiFi radio on or off.
+
+    Body: {"enabled": bool, "force": bool (optional)}. Disabling is refused
+    unless Ethernet is connected or force=True, to avoid locking the user out
+    of this web interface.
+    """
+    try:
+        from src.wifi_manager import WiFiManager
+
+        data = request.get_json(silent=True) or {}
+        if 'enabled' not in data:
+            return jsonify({
+                'status': 'error',
+                'message': 'enabled is required'
+            }), 400
+
+        # Parse defensively: bool("false") is True, so mirror the string-aware
+        # coercion used for `force` — the endpoint is a public contract, not just
+        # the shipped UI (which always sends real JSON booleans).
+        _enabled_raw = data['enabled']
+        enabled = _enabled_raw is True or (isinstance(_enabled_raw, str) and _enabled_raw.lower() in ('true', '1', 'yes'))
+        _force_raw = data.get('force', False)
+        force = _force_raw is True or (isinstance(_force_raw, str) and _force_raw.lower() in ('true', '1', 'yes'))
+
+        wifi_manager = WiFiManager()
+        success, message, reason = wifi_manager.set_wifi_radio(enabled, force=force)
+
+        if success:
+            return jsonify({
+                'status': 'success',
+                'message': message,
+                'data': wifi_manager.get_wifi_radio_state()
+            })
+        else:
+            return jsonify({
+                'status': 'error',
+                'message': message,
+                'reason': reason
+            }), 400
+    except Exception as e:
+        logger.error("Error setting WiFi radio state", exc_info=True)
+        return jsonify({
+            'status': 'error',
+            'message': 'An error occurred; see logs for details'
+        }), 500
+
 @api_v3.route('/cache/list', methods=['GET'])
 def list_cache_files():
     """List all cache files with metadata"""