launcher: Photon AppId setup walkthrough

The two empty "REALTIME APPID / VOICE APPID" textboxes assumed the
user already knew what Photon was, where to sign up, and which app
type to create. New 5-step wizard fills that gap:

1. What's Photon? — one-paragraph explanation tying back to DorkNet
2. Make an account — Open Dashboard button launches browser
3. Create a Realtime app — numbered click-by-click instructions
4. Create a Voice app — same, with a Skip button (voice is optional)
5. Paste your AppIds — text fields with live regex validation,
   region picker, Save commits to AppState

Hyphens optional on input; we normalise to canonical 8-4-4-4-12 form
before writing back. The existing Photon section keeps its three
fields for advanced users, with a "Setup walkthrough" button at the
top opening the wizard prefilled with current values.

launcher/MainWindow.xaml

@@ -174,14 +174,20 @@
                         <!-- Photon panel -->
                         <Border Style="{StaticResource Panel}" Margin="0,0,0,16">
                             <StackPanel>
-                                <TextBlock Style="{StaticResource SectionTitle}" Text="Photon AppIds" />
+                                <Grid Margin="0,0,0,12">
+                                    <TextBlock Style="{StaticResource SectionTitle}"
+                                               Text="Photon AppIds" Margin="0" />
+                                    <Button HorizontalAlignment="Right" Style="{StaticResource Btn}"
+                                            Content="Setup walkthrough" Click="OnOpenPhotonWizard"
+                                            Padding="14,6" FontSize="12" />
+                                </Grid>
                                 <TextBlock Foreground="{StaticResource InkSoft}" FontSize="12"
-                                           Margin="0,-8,0,12" TextWrapping="Wrap">
+                                           Margin="0,0,0,12" TextWrapping="Wrap">
                                     Photon Cloud powers in-room realtime sync. Free to register at
                                     <Hyperlink NavigateUri="https://dashboard.photonengine.com"
                                                Foreground="{StaticResource Brand}"
                                                RequestNavigate="OnNavigate">dashboard.photonengine.com</Hyperlink>;
-                                    DorkNet never bundles one.
+                                    DorkNet never bundles one. First time? Click "Setup walkthrough" above.
                                 </TextBlock>
 
                                 <TextBlock Style="{StaticResource FieldLabel}" Text="REALTIME APPID" />