ci: Upgrade macOS runner versions to macOS 15

- Update build-macos-x64 runner from macos-13 to macos-15
- Update build-macos-arm64 runner from macos-14 to macos-15

This ensures both Intel and Apple Silicon builds use the latest
macOS 15 runners for consistency and access to updated tooling.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: MarkoVcode

.github/workflows/brunon-release.yml

@@ -105,7 +105,7 @@ jobs:
 
   build-macos-x64:
     name: Build macOS (Intel)
-    runs-on: macos-13
+    runs-on: macos-15
     permissions:
       contents: read
     env:
@@ -149,7 +149,7 @@ jobs:
 
   build-macos-arm64:
     name: Build macOS (Apple Silicon)
-    runs-on: macos-14
+    runs-on: macos-15
     permissions:
       contents: read
     env: