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/tailwind.config.cjs

@@ -6,7 +6,59 @@ module.exports = {
   ],
   darkMode: 'class',
   theme: {
-    extend: {},
+    extend: {
+      colors: {
+        // === certctl brand palette (from logo) ===
+        brand: {
+          50:  '#eefbf6',
+          100: '#d5f5e9',
+          200: '#afe9d5',
+          300: '#7ad8bc',
+          400: '#2ea88f', // Primary teal — logo "ctl"
+          500: '#1f9680',
+          600: '#147868',
+          700: '#106055',
+          800: '#0f4d44',
+          900: '#0d3f39',
+        },
+        accent: {
+          blue:   '#3b7dd8', // Logo blue arrows
+          orange: '#e8873a', // Logo orange arrows
+          green:  '#4ebe6e', // Logo green highlights
+        },
+        // Light content area
+        page:    '#f0f4f8',  // Light blue-gray page background
+        surface: {
+          DEFAULT: '#ffffff', // Cards — white
+          hover:   '#f8fafc', // Hover on cards
+          border:  '#e2e8f0', // Card/table borders
+          muted:   '#f1f5f9', // Zebra stripes, subtle fills
+        },
+        // Dark sidebar
+        sidebar: {
+          DEFAULT: '#0c2e25', // Deep teal-black
+          hover:   '#134438',
+          active:  '#185c4a',
+          border:  '#1a5c48',
+          text:    '#94d2be', // Muted teal for inactive nav
+        },
+        // Text on light backgrounds
+        ink: {
+          DEFAULT: '#1e293b', // Primary text
+          muted:   '#64748b', // Secondary text
+          faint:   '#94a3b8', // Tertiary/placeholder
+        },
+      },
+      fontFamily: {
+        mono: ['JetBrains Mono', 'ui-monospace', 'SFMono-Regular', 'Menlo', 'Monaco', 'Consolas', 'monospace'],
+      },
+      borderRadius: {
+        DEFAULT: '0.375rem',
+        sm: '0.25rem',
+        md: '0.5rem',
+        lg: '0.75rem',
+      },
+    },
   },
   plugins: [],
 }