feat: dashboard theme overhaul — light content area with branded teal sidebar

Complete frontend visual redesign using certctl logo color palette:
- Deep teal sidebar (#0c2e25) with prominent centered logo (64px in white pill)
- Light content area (#f0f4f8) with white cards and visible borders
- Brand colors from logo: teal (#2ea88f), blue (#3b7dd8), orange (#e8873a), green (#4ebe6e)
- Inter + JetBrains Mono typography, colored stat card top borders
- All 17 pages + 7 components updated (25 files, ~700 lines changed)
- 15 new dashboard screenshots replacing old dark theme screenshots
- Prometheus metrics e2e test added, integration test mock fixes
- Docs updated: architecture.md theme description, testing-guide.md DNS-PERSIST-01 coverage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/components/ErrorBoundary.tsx

@@ -26,10 +26,10 @@ export default class ErrorBoundary extends Component<Props, State> {
   render() {
     if (this.state.hasError) {
       return (
-        <div className="flex items-center justify-center min-h-screen bg-slate-900">
+        <div className="flex items-center justify-center min-h-screen bg-page">
           <div className="text-center p-8">
-            <h1 className="text-xl font-semibold text-red-400 mb-2">Something went wrong</h1>
-            <p className="text-sm text-slate-400 mb-4">
+            <h1 className="text-xl font-semibold text-red-700 mb-2">Something went wrong</h1>
+            <p className="text-sm text-ink-muted mb-4">
               {this.state.error?.message || 'An unexpected error occurred'}
             </p>
             <button
@@ -37,7 +37,7 @@ export default class ErrorBoundary extends Component<Props, State> {
                 this.setState({ hasError: false, error: null });
                 window.location.reload();
               }}
-              className="px-4 py-2 bg-blue-600 text-white rounded-lg text-sm hover:bg-blue-500"
+              className="px-4 py-2 bg-brand-500 text-white rounded text-sm hover:bg-brand-600"
             >
               Reload Page
             </button>