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/.gitignore

@@ -0,0 +1,115 @@
+# Dependencies
+**/node_modules
+.pnpm-store/
+
+# Build outputs
+dist/
+build/
+*.dist
+
+# Environment variables
+.env
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# IDE and editor files
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS generated files
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Coverage directory used by tools like istanbul
+coverage/
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Dependency directories
+jspm_packages/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+
+# Nuxt.js build / generate output
+.nuxt
+
+# Gatsby files
+.cache/
+
+# Storybook build outputs
+.out
+.storybook-out
+
+# Temporary folders
+tmp/
+temp/
+
+# Database
+*.db
+*.sqlite
+*.sqlite3
+
+# Webdev artifacts (checkpoint zips, migrations, etc.)
+.webdev/
+
+# Manus version file (auto-generated, not part of source)
+client/public/__manus__/version.json
+
+# Manus dev tooling (browser console / network logs)
+.manus-logs/