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/patches/wouter@3.7.1.patch

@@ -0,0 +1,28 @@
+diff --git a/esm/index.js b/esm/index.js
+index c83bc63a2c10431fb62e25b7d490656a3796f301..bcae513cc20a4be6c38dc116e0b8d9bacda62b5b 100644
+--- a/esm/index.js
++++ b/esm/index.js
+@@ -338,6 +338,23 @@ const Switch = ({ children, location }) => {
+   const router = useRouter();
+   const [originalLocation] = useLocationFromRouter(router);
+ 
++  // Collect all route paths to window object
++  if (typeof window !== 'undefined') {
++    if (!window.__WOUTER_ROUTES__) {
++      window.__WOUTER_ROUTES__ = [];
++    }
++
++    const allChildren = flattenChildren(children);
++    allChildren.forEach((element) => {
++      if (isValidElement(element) && element.props.path) {
++        const path = element.props.path;
++        if (!window.__WOUTER_ROUTES__.includes(path)) {
++          window.__WOUTER_ROUTES__.push(path);
++        }
++      }
++    });
++  }
++
+   for (const element of flattenChildren(children)) {
+     let match = 0;
+