Add Prism Launcher (Minecraft) to first-boot flatpaks

Microsoft account sign-in documented in OPERATIONS.md; Prism manages
its own Java runtimes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

recipes/bc250-console-gnome.yml

@@ -34,6 +34,7 @@ modules:
         - net.davidotek.pupgui2 # ProtonUp-Qt: Proton-GE manager
         - com.heroicgameslauncher.hgl # Heroic: Epic + GOG
         - net.retrodeck.retrodeck # RetroDECK: retro emulation
+        - org.prismlauncher.PrismLauncher # Minecraft (Java; sign in with Microsoft account)
 
   - type: systemd
     system: