feat(frontend): add Front/ — Vite/React frontend with backend pipeline integration

Mirror of design_agent_front/design-agent/ for shipping alongside backend.

Vite plugin (vitePluginPhaseZApi) endpoints :
  - POST /api/run   — spawn `python -m src.phase_z2_pipeline` with overrides
  - GET  /api/sample-mdx?mdx=03/04/05 — fixed sample MDX
  - GET  /frame-preview/{n} — figma preview thumbnails
  - GET  /data/runs/{run_id}/{path} — pipeline artifacts (final.html, step*.json, ...)

Env toggle forward (보고용) :
  PHASE_Z_ALLOW_RESTRUCTURE / PHASE_Z_ALLOW_REJECT / PHASE_Z_MAX_RANK=32

Components :
  - LeftMdxPanel (03/04/05 fix list + section tree)
  - SlideCanvas (iframe + slideOverrideCss prop for inline CSS inject)
  - FramePanel (label priority + confidence sort)
  - LayoutPanel

README with mermaid diagrams covering the 5-step demo flow.
node_modules / dist / .manus-logs / .env excluded via .gitignore.

Front/client/src/App.tsx

@@ -0,0 +1,30 @@
+import { TooltipProvider } from "@/components/ui/tooltip";
+import NotFound from "@/pages/NotFound";
+import { Route, Switch } from "wouter";
+import ErrorBoundary from "./components/ErrorBoundary";
+import { ThemeProvider } from "./contexts/ThemeContext";
+import Home from "./pages/Home";
+
+function Router() {
+  return (
+    <Switch>
+      <Route path={"/"} component={Home} />
+      <Route path={"/404"} component={NotFound} />
+      <Route component={NotFound} />
+    </Switch>
+  );
+}
+
+function App() {
+  return (
+    <ErrorBoundary>
+      <ThemeProvider defaultTheme="light">
+        <TooltipProvider>
+          <Router />
+        </TooltipProvider>
+      </ThemeProvider>
+    </ErrorBoundary>
+  );
+}
+
+export default App;