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.

backend/pyproject.toml

@@ -0,0 +1,28 @@
+[project]
+name = "fraudshield"
+version = "0.1.0"
+description = "Motor de detecção de fraudes bancárias"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi[standard]>=0.115.0",
+    "uvicorn[standard]>=0.32.0",
+    "sqlalchemy[asyncio]>=2.0.36",
+    "asyncpg>=0.30.0",
+    "alembic>=1.14.0",
+    "pydantic-settings>=2.6.0",
+    "redis[hiredis]>=5.2.0",
+    "python-jose[cryptography]>=3.3.0",
+    "passlib[bcrypt]>=1.7.4",
+    "structlog>=24.4.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.3.0",
+    "pytest-asyncio>=0.24.0",
+    "httpx>=0.28.0",
+]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]