Initial MVP skeleton with auth, chat persistence, UI and text LLM integration

backend/app/main.py

@@ -0,0 +1,59 @@
+from pathlib import Path
+
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.health import router as health_router
+from app.api.auth import router as auth_router
+from app.api.chats import router as chats_router
+from app.core.config import settings
+from app.db.init_db import init_db
+from app.db.session import SessionLocal
+
+
+def ensure_dirs() -> None:
+    for path in [settings.upload_root, settings.temp_root, settings.log_root]:
+        Path(path).mkdir(parents=True, exist_ok=True)
+
+
+ensure_dirs()
+
+app = FastAPI(
+    title="AI Chat MVP Backend",
+    version="0.1.0",
+)
+
+
+@app.on_event("startup")
+def on_startup():
+    db = SessionLocal()
+    try:
+        init_db(db)
+    finally:
+        db.close()
+
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=[
+        "http://127.0.0.1:13000",
+        "http://localhost:13000",
+        "http://192.168.149.194:13000",
+    ],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+app.include_router(health_router, prefix="/api")
+app.include_router(auth_router, prefix="/api/auth", tags=["auth"])
+app.include_router(chats_router, prefix="/api", tags=["chats"])
+
+
+@app.get("/")
+def root() -> dict:
+    return {
+        "service": "ai-chat-backend",
+        "env": settings.app_env,
+        "docs": "/docs",
+    }