chore(deps): consolidate dependencies, configure dependabot groups, and bump to v3.15.1

[spelech]

Summary

• Consolidates all open Dependabot updates across NuGet, npm, and GitHub Actions into a single verified branch.
• Configures \groups\ in .github/dependabot.yml\ for all package ecosystems so future updates are submitted as consolidated batches rather than individual PRs.
• Bumps project version to \3.15.1\ and synchronizes compiled Avalonia WebAssembly distribution in \wwwroot/_framework/.

Dependency Updates Included

• GitHub Actions:
  • \�ctions/checkout@v7\
  • \�ctions/setup-dotnet@v6\
  • \�ctions/setup-node@v7\
  • \�ctions/upload-pages-artifact@v5\
  • \�ctions/deploy-pages@v5\
  • \softprops/action-gh-release@v3\
  • \docker/setup-buildx-action@v4\
  • \docker/build-push-action@v7\
• NuGet:
  • \Microsoft.Extensions.Hosting.WindowsServices\ (10.0.11 -> 10.0.12)
  • \Microsoft.Extensions.Http\ (10.0.11 -> 10.0.12)
  • \System.Management\ (10.0.11 -> 10.0.12)
  • \Microsoft.NET.Test.Sdk\ (18.9.0 -> 18.10.1)
  • \Microsoft.Playwright\ (1.50.0 -> 1.62.0)
• NPM:
  • \�slint\ (9.39.5 -> 10.10.0)
  • @eslint/js\ (9.39.5 -> 10.0.1)
  • \ ypescript-eslint\ (8.67.0 -> 8.70.0)
  • @playwright/test\ (1.62.1 -> 1.63.0)
  • @types/node\ (22.20.1 -> 26.6.1)
  • \playwright-layout-inspector\ (\d63b246\ -> \c042a04)

Verification

• 
  pm run lint\ (eslint .) passed cleanly.
• 
  px tsc --noEmit\ passed cleanly.
• 
  pm run docs:build\ passed cleanly.
• \dotnet test\ (732 passed, 0 failed, 6 skipped).
• Wasm asset freshness and headless Avalonia interaction tests passed.