Add multi-user authentication with JWT

- Users table with email/bcrypt-hashed password; register and login via /auth/ endpoints
- JWT tokens (30-day expiry) stored in localStorage; all API routes require Bearer auth
- All data (varieties, batches, settings, notification logs) scoped to the authenticated user
- Login/register screen overlays the app; sidebar shows user email and logout button
- Scheduler sends daily ntfy summaries for every configured user
- DB schema rewritten for multi-user; SECRET_KEY added to env

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/auth.py

@@ -0,0 +1,33 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from auth import create_access_token, get_current_user, hash_password, verify_password
+from database import get_db
+from models import User
+from schemas import Token, UserCreate, UserLogin, UserOut
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+@router.post("/register", response_model=UserOut, status_code=201)
+def register(data: UserCreate, db: Session = Depends(get_db)):
+    if db.query(User).filter(User.email == data.email).first():
+        raise HTTPException(status_code=400, detail="Email already registered")
+    user = User(email=data.email, hashed_password=hash_password(data.password))
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+    return user
+
+
+@router.post("/login", response_model=Token)
+def login(data: UserLogin, db: Session = Depends(get_db)):
+    user = db.query(User).filter(User.email == data.email).first()
+    if not user or not verify_password(data.password, user.hashed_password):
+        raise HTTPException(status_code=401, detail="Invalid email or password")
+    return {"access_token": create_access_token(user.id), "token_type": "bearer"}
+
+
+@router.get("/me", response_model=UserOut)
+def me(current_user: User = Depends(get_current_user)):
+    return current_user