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/App.xaml

@@ -240,6 +240,15 @@
             <Setter Property="FontFamily" Value="Segoe UI Variable, Segoe UI" />
         </Style>
 
+        <!-- Numbered-step bullet used in walkthrough text. -->
+        <Style x:Key="StepBullet" TargetType="TextBlock">
+            <Setter Property="Foreground" Value="{StaticResource Ink}" />
+            <Setter Property="FontSize" Value="13" />
+            <Setter Property="LineHeight" Value="22" />
+            <Setter Property="Margin" Value="0,0,0,6" />
+            <Setter Property="TextWrapping" Value="Wrap" />
+        </Style>
+
         <!-- Pill-style "status chip" used in section headers. -->
         <Style x:Key="StatusChip" TargetType="Border">
             <Setter Property="Background" Value="{StaticResource BgElev2}" />