frontend: scaffold Vite + React 19 + TS + Tailwind v4 + TanStack Query

Bare-minimum SPA that wires up to the FastAPI backend:

- Vite 6 + React 19 + TS strict, alias @/* to src/*
- Tailwind v4 via @tailwindcss/vite (no postcss)
- TanStack Query v5 with sane defaults (30s staleTime, no auto-refetch)
- React Router 7 for routing
- ECharts + Recharts available (charts land in Phase 1a)
- Vitest + @testing-library/react for tests
- Dev proxy /api → http://localhost:8080 (FastAPI)

Pages:
- Dashboard — pulls /networth, shows total + per-account cards.
  No chart yet (Phase 1a). Empty/error states for "no data" cases
  point users to the ingest CLI.

Header shows live API health (queue depth from /healthz). 274 KB JS
gzipped to 87 KB. typecheck + build pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/package.json

@@ -0,0 +1,45 @@
+{
+  "name": "fire-planner-frontend",
+  "private": true,
+  "version": "0.0.1",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "preview": "vite preview",
+    "lint": "eslint .",
+    "typecheck": "tsc -b --noEmit",
+    "test": "vitest run",
+    "test:watch": "vitest"
+  },
+  "dependencies": {
+    "@tanstack/react-query": "^5.62.0",
+    "echarts": "^6.0.0",
+    "echarts-for-react": "^3.0.2",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "react-router-dom": "^7.1.0",
+    "recharts": "^3.0.0",
+    "zustand": "^5.0.0"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.0.0",
+    "@testing-library/jest-dom": "^6.6.0",
+    "@testing-library/react": "^16.1.0",
+    "@testing-library/user-event": "^14.5.0",
+    "@types/node": "^22.10.0",
+    "@types/react": "^19.0.0",
+    "@types/react-dom": "^19.0.0",
+    "@vitejs/plugin-react": "^4.3.0",
+    "eslint": "^9.17.0",
+    "eslint-plugin-react-hooks": "^5.1.0",
+    "eslint-plugin-react-refresh": "^0.4.0",
+    "globals": "^15.14.0",
+    "jsdom": "^26.0.0",
+    "tailwindcss": "^4.0.0",
+    "typescript": "^5.7.0",
+    "typescript-eslint": "^8.18.0",
+    "vite": "^6.0.0",
+    "vitest": "^3.0.0"
+  }
+}