feat: complete UI/UX overhaul with Impeccable design system

Replace Inter/Baskerville with self-hosted Manrope/Alegreya/JetBrains Mono
variable fonts. Migrate all colors from hex to OKLCH tokens (30+ CSS custom
properties) with full dark/light mode support. Replace Unicode emoji with
lucide-react SVG icons throughout. Convert all page layouts to inline styles
(Tailwind CSS 4 flex/grid classes unreliable in this project). Code-split
routes via React.lazy (760KB → 15KB initial shell + 10 lazy chunks).

Add global styles: scrollbar theming, selection color, input/button bases,
:focus-visible ring, prefers-reduced-motion. Setup wizard gets 4-phase
indicator with numbered circles, PathInput and StatusDot components.
Toast container gets aria-live="polite". Tab close buttons changed to
proper <button> elements with aria-labels.

All 8 pages (Dashboard, Editor, Build, Server, Toolset, Repos, Settings,
Setup) rewritten with consistent card/section/button patterns.

packages/frontend/package.json

@@ -9,9 +9,13 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "@fontsource-variable/alegreya": "^5.2.8",
+    "@fontsource-variable/jetbrains-mono": "^5.2.8",
+    "@fontsource-variable/manrope": "^5.2.8",
     "@monaco-editor/react": "^4.7.0",
     "@xterm/addon-fit": "^0.11.0",
     "@xterm/xterm": "^6.0.0",
+    "lucide-react": "^1.8.0",
     "monaco-editor": "^0.55.1",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",