ci: switch iOS and Android builds to mini runner

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: pythoninthegrass

.github/workflows/build-android-app.yml

@@ -29,7 +29,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: studio
+    runs-on: mini
     env:
       BUNDLE_FROZEN: "true"
       RUBYOPT: "-W0"

.github/workflows/build-ios-app.yml

@@ -29,7 +29,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: studio
+    runs-on: mini
     env:
       BUNDLE_FROZEN: "true"
       RUBYOPT: "-W0"