feat(modpackchecker): Add Gemini-designed extension icon

- Isometric cube with checkmark (version check concept)
- Frost (#4ECDC4) edge on left, Fire (#FF6B35) edge on right
- Subtle Firefrost branding that fits Pterodactyl's UI
- 128x128 PNG with transparency

Designed by Gemini AI, April 2026.

Signed-off-by: Claude (Chronicler #63) <claude@firefrostgaming.com>

services/modpack-version-checker/blueprint-extension/conf.yml

@@ -6,7 +6,7 @@ info:
   version: "1.0.0"
   target: "beta-2026-01"
   author: "Firefrost Gaming <dev@firefrostgaming.com>"
-  icon: ""
+  icon: "icon.png"
   website: "https://firefrostgaming.com"
 admin:
   view: "admin/view.blade.php"