feat: setup FastAPI main app with routers and test fixtures

- Main FastAPI app with all routers included
- CORS middleware for frontend
- Test fixtures with in-memory SQLite database
- Placeholder routers for future tasks

backend/app/main.py

@@ -1,7 +1,8 @@
 from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
 from contextlib import asynccontextmanager
 from app.database import engine, Base
-from app.routers import sources, jobs
+from app.routers import sources, jobs, executions, backups, settings, dashboard
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
@@ -9,7 +10,27 @@ async def lifespan(app: FastAPI):
         await conn.run_sync(Base.metadata.create_all)
     yield
 
-app = FastAPI(title="Backup Tool API", lifespan=lifespan)
+app = FastAPI(
+    title="Backup Tool API",
+    version="0.1.0",
+    lifespan=lifespan
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["http://localhost:3000"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
 
 app.include_router(sources.router)
 app.include_router(jobs.router)
+app.include_router(executions.router)
+app.include_router(backups.router)
+app.include_router(settings.router)
+app.include_router(dashboard.router)
+
+@app.get("/api/health")
+async def health_check():
+    return {"status": "healthy"}