fix(network): fix wifi page never scanning, never exiting, and UI freezes on connect

WiFiSetupPage never showed networks and could not be exited once entered.
Several compounding bugs were responsible across network.go and page.go.

Primary bugs fixed:

- WiFiSetupPage.Init() never assigned p.wifiDevice after FindDevices(),
  so startScan() always hit the nil guard and exited without launching
  a scan goroutine. No networks ever appeared in the list. A value copy
  of the Wi-Fi device is now taken from m.Devices immediately after
  FindDevices() returns, with an explicit error if no adapter is found.

- CheckInternetConnection() called FindDevices() on every tick, rebuilding
  m.Devices every 2 seconds. This caused [NET-030] log spam, invalidated
  any pointers held into the slice, and meant checkState()'s fresh Manager
  instances (which have an empty Devices slice) would never detect internet
  after Fix 2 was applied. CheckInternetConnection() now calls FindDevices()
  only when m.Devices is empty (fresh Manager), and does a cheaper per-device
  State property refresh when devices are already known (long-lived Manager).
  This satisfies both callers correctly.

- Connect() called WaitForInternet(30s, 5s) synchronously before returning,
  blocking the main UI thread for up to 35 seconds. It also returned an error
  if internet wasn't stable in time, even though AddAndActivateConnection had
  succeeded, causing the page to show "Failed to initiate connection" while NM
  was still negotiating in the background. WaitForInternet removed from
  Connect(); the page's existing checkConnectionStatusLoop and
  handleConnectionStatusUpdate already handle post-connection state tracking.

Additional bugs fixed:

- startScan() launched a new StartScan goroutine on every R-press without
  signalling the previous one to stop. Concurrent goroutines raced on
  resultsChan and accumulated indefinitely. stopScan is now closed and
  replaced before each scan, and checkConnectionStatusLoop is restarted
  with the new channel.

- Connect() always generated a new UUID and called AddAndActivateConnection
  without checking for an existing profile. Repeated connection attempts
  (e.g. wrong password then correct) accumulated duplicate stale profiles
  in NetworkManager. Existing profiles matching the SSID are now deleted
  via Settings.Connection.Delete before creating a new one.

- m.Devices was read and written concurrently from StartScan and
  CheckInternetConnection goroutines without synchronisation. A sync.RWMutex
  is added to Manager; state refreshes take a write lock, StartScan device
  lookup takes a read lock.

- Connect() checked wifiDevice.State using the caller's value copy taken at
  Init() time, which never updated. The current state is now read from
  m.Devices under lock at the point of connection.

- auth-alg: "open" was unconditionally set in the 802-11-wireless-security
  settings block. This field is only meaningful for WPA/WPA2-Personal and
  should be omitted for SAE (WPA3) and EAP variants. It is now only set
  when KeyMgmt is "wpa-psk".

internal/page/wifiSetupPage.go

@@ -97,8 +97,23 @@ func (p *WiFiSetupPage) Init(ctx *PageCtx) error {
 		return fmt.Errorf("failed to find network devices: %w. Try rebooting the computer. If this is your 3rd reboot, call for help", err)
 	}
 
+	// FindDevices() rebuilds m.Devices each call, so store a VALUE copy,
+	// not a pointer into the slice — it would be invalidated on next call.
+	for i := range p.networkManager.Devices {
+		if p.networkManager.Devices[i].Type == network.TypeWifi {
+			device := p.networkManager.Devices[i]
+			p.wifiDevice = &device
+			break
+		}
+	}
+	if p.wifiDevice == nil {
+		p.networkManager.Close()
+		p.networkManager = nil
+		return fmt.Errorf("no Wi-Fi adapter found. Try rebooting the computer. If this is your 3rd reboot, call for help")
+	}
+
 	// Create UI elements
-	white := sdl.Color{R: 255, G: 255, B: 255, A: 255}
+	white := colors.White
 	p.titleItem, err = NewStringItem("Wi-Fi Setup", p.applicationFont, white)
 	if err != nil {
 		return fmt.Errorf("failed to create title item: %w", err)
@@ -117,7 +132,6 @@ func (p *WiFiSetupPage) Init(ctx *PageCtx) error {
 
 	// Start scanning and status monitoring
 	p.startScan()
-	go p.checkConnectionStatusLoop()
 
 	return nil
 }
@@ -143,6 +157,11 @@ func (p *WiFiSetupPage) checkConnectionStatusLoop() {
 
 // startScan triggers a new asynchronous network scan.
 func (p *WiFiSetupPage) startScan() {
+	if p.stopScan != nil {
+		close(p.stopScan)
+	}
+	p.stopScan = make(chan struct{})
+
 	p.isScanning = true
 	p.selectedIndex = 0
 	p.scrollOffset = 0
@@ -150,6 +169,7 @@ func (p *WiFiSetupPage) startScan() {
 
 	if p.wifiDevice != nil {
 		go p.networkManager.StartScan(p.resultsChan, p.errorChan, p.stopScan)
+		go p.checkConnectionStatusLoop()
 	} else {
 		p.isScanning = false
 	}