Add Portal Settings Web Part with styles, localization, and tests

- Implemented the PortalSettings Web Part with a new manifest and TypeScript file.
- Created SCSS styles for the Web Part, defining various UI elements and responsive design.
- Added localization support for English and German languages.
- Developed tests for Provider Registry and static assets validation.
- Included PowerShell script for project validation.

tests/validate-static-assets.js

@@ -0,0 +1,36 @@
+'use strict';
+
+var fs = require('fs');
+var path = require('path');
+var root = path.resolve(__dirname, '..');
+var passed = 0;
+
+function read(file) { return fs.readFileSync(path.join(root, file), 'utf8'); }
+function json(file) { return JSON.parse(read(file)); }
+function assert(condition, message) { if (!condition) { throw new Error(message); } passed++; }
+
+var packageJson = json('package.json');
+var solution = json('config/package-solution.json').solution;
+var config = json('config/config.json');
+var manifest = json('src/webparts/portalSettings/PortalSettingsWebPart.manifest.json');
+var styles = read('src/webparts/portalSettings/PortalSettings.scss');
+var sourceFiles = [
+  'src/ui/Dom.ts',
+  'src/ui/DynamicFormRenderer.ts',
+  'src/ui/PortalSettingsApp.ts'
+].map(read).join('\n');
+
+assert(packageJson.version === '3.0.0', 'Package-Version ist nicht 3.0.0.');
+assert(solution.version === '3.0.0.0', 'Solution-Version ist nicht 3.0.0.0.');
+assert(!solution.features, 'Alte ASPX-Feature-Assets sind noch registriert.');
+assert(!!config.bundles['portal-settings-web-part'], 'WebPart-Bundle fehlt.');
+assert(manifest.componentType === 'WebPart', 'Komponente ist kein WebPart.');
+assert(!fs.existsSync(path.join(root, 'src/assets/PortalSettings.aspx')), 'Alte ASPX-Seite ist noch vorhanden.');
+assert(!fs.existsSync(path.join(root, 'src/extensions/portalSettings/PortalSettingsApplicationCustomizer.ts')), 'Alter Application Customizer ist noch vorhanden.');
+assert(sourceFiles.indexOf('innerHTML') < 0, 'UI darf innerHTML nicht verwenden.');
+['themePrimary', 'neutralPrimary', 'neutralLight', 'white'].forEach(function (slot) {
+  assert(styles.indexOf('[theme: ' + slot + ', default:') >= 0, 'Themeslot fehlt: ' + slot);
+});
+assert(packageJson.scripts.package.indexOf('npm test') === 0, 'Paketierung startet nicht mit Tests.');
+
+console.log('PortalSettings static tests passed: ' + passed);