feat: add Nova 5 support

[alies-dev]

Summary

• composer.json: Bump PHP to ^8.1, move laravel/nova to require-dev at ^5.0, add laravel/nova-devtool ^1.7 and illuminate/support, remove hardcoded Nova repository URL
• Asset registration: Switch from Nova::script() to Nova::mix() with mix-manifest.json for proper cache-busting
• Build system: Use laravel-nova-devtool Mix extension instead of manual webpack externals config
• package.json: Remove vue-loader, vue-template-compiler, and vue (provided externally by Nova), add nova:install script
• Vue components: Replace removed <default-button> Nova component with native <button>/<a> elements
• JS entry point: Update Nova.booting() callback signature from (Vue) to (app, store) per Nova 5 convention
• Service provider: Add route cache guard, modernize PHP with return types

Test plan

• Run composer install in a Nova 5 project with this package
• Run npm run nova:install && npm install && npm run prod to build assets
• Verify all chart types render on a Nova dashboard (Bar, Stacked, Line/Area, Doughnut, Pie, PolarArea, Scatter)
• Verify refresh/reload buttons work
• Verify external link buttons work
• Verify filter dropdowns work with model-based charts
• Verify data labels plugin works when enabled