backend: add FastAPI scaffold, models, oauth flow, schema

modern/backend/app.py

@@ -0,0 +1,43 @@
+from fastapi import FastAPI, Depends, HTTPException
+from fastapi.middleware.cors import CORSMiddleware
+from . import models
+from .oauth import router as oauth_router
+import os
+
+app = FastAPI(title='LifeRPG Modern Backend')
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=[os.getenv('FRONTEND_ORIGIN', 'http://localhost:5173')],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+@app.on_event('startup')
+def startup_event():
+    models.init_db()
+
+@app.get('/health')
+def health():
+    return {'status': 'ok'}
+
+@app.get('/api/v1/hello')
+def hello():
+    return {'message': 'Hello from LifeRPG modern backend (FastAPI)'}
+
+app.include_router(oauth_router, prefix='/api/v1')
+
+# Basic user routes (demo)
+@app.post('/api/v1/users')
+def create_user(payload: dict):
+    db = models.SessionLocal()
+    email = payload.get('email')
+    if not email:
+        raise HTTPException(status_code=400, detail='email required')
+    user = models.User(email=email, display_name=payload.get('display_name'))
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+    db.close()
+    return {'id': user.id, 'email': user.email}