feat: implement FraudShield MVP — backend API + frontend alerts

Backend (Python 3.12/FastAPI):
- 5 models: Transaction, DetectionRule, FraudAlert, AuditLog, RuleSnapshot
- Rule engine: 4 rule types (amount, location, time, pattern)
- 11 API routes: health, auth, transactions, alerts
- Sync ingestion pipeline with explanation generation
- JWT auth with 3 roles (analyst, admin, senior)
- Seed script with 5 default rules + 50 synthetic transactions

Frontend (React 19/TypeScript/Tailwind):
- Auth: login page, JWT token management, role-based routing
- Alerts: queue with filters, detail panel, decision workflow
- Layout: responsive sidebar, top bar, protected routes
- Full TypeScript, zero ts-ignore, Tailwind CSS

Build: Backend imports clean, Frontend tsc --noEmit passes,
vite build produces 296KB production bundle.

frontend/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "fraudshield-frontend",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "react-router-dom": "^7.0.0",
+    "@tanstack/react-query": "^5.0.0",
+    "recharts": "^2.15.0",
+    "lucide-react": "^0.460.0",
+    "clsx": "^2.1.0"
+  },
+  "devDependencies": {
+    "@types/react": "^19.0.0",
+    "@types/react-dom": "^19.0.0",
+    "@vitejs/plugin-react": "^4.3.0",
+    "autoprefixer": "^10.4.0",
+    "postcss": "^8.4.0",
+    "tailwindcss": "^3.4.0",
+    "typescript": "~5.6.0",
+    "vite": "^6.0.0"
+  }
+}