feat: Add custom branding functionality with CSS and JSON configuration

- Introduced custom branding CSS styles in `custom-branding.css`.
- Created example JSON configuration for custom branding in `custom-branding.example.json`.
- Implemented branding configuration logic in `BrandingConfig.ts` to normalize and validate branding settings.
- Developed CSS loader to manage loading and unloading of custom stylesheets in `BrandingCssLoader.ts`.
- Added DOM rendering capabilities for branding elements in `BrandingDomRenderer.ts`.
- Defined types and interfaces for branding elements and configurations in `BrandingTypes.ts`.
- Included localization support for German in `de-de.js`.
- Added unit tests for branding configuration, CSS loader, and DOM renderer.
- Validated project structure and static assets with new validation scripts.

build-classic.ps1

@@ -0,0 +1,25 @@
+param(
+    [string]$OutputPath = ''
+)
+
+$sourcePath = Join-Path $PSScriptRoot 'classic'
+$resolvedOutputPath = if ([string]::IsNullOrWhiteSpace($OutputPath)) {
+    Join-Path $sourcePath 'dist'
+}
+else {
+    $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($OutputPath)
+}
+
+if (-not (Test-Path -LiteralPath $resolvedOutputPath)) {
+    New-Item -ItemType Directory -Path $resolvedOutputPath -Force | Out-Null
+}
+
+foreach ($file in @('custom-branding-classic.js', 'classic-deployment.md')) {
+    $source = Join-Path $sourcePath $file
+    if (-not (Test-Path -LiteralPath $source)) { throw ('Classic-Datei fehlt: ' + $source) }
+    Copy-Item -LiteralPath $source -Destination (Join-Path $resolvedOutputPath $file) -Force
+    Write-Host ('Kopiert: ' + $file) -ForegroundColor Green
+}
+
+Write-Host ('Classic-Paket erstellt: ' + $resolvedOutputPath) -ForegroundColor Green
+