feat: scaffold FastAPI app, config, and SQLite models

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/main.py

@@ -0,0 +1,23 @@
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from app.config import settings
+from app.db import Base, engine
+from app import models  # noqa: F401 — register models with Base.metadata
+
+
+@asynccontextmanager
+async def lifespan(_app: FastAPI):
+    settings.data_dir.mkdir(parents=True, exist_ok=True)
+    settings.uploads_dir.mkdir(parents=True, exist_ok=True)
+    Base.metadata.create_all(bind=engine)
+    yield
+
+
+app = FastAPI(title="MincedPad", lifespan=lifespan)
+
+
+@app.get("/api/health")
+def health():
+    return {"ok": True, "name": "MincedPad"}