Add rate limiting to login endpoint

Security:
- Add slowapi dependency for rate limiting
- Create rate_limit.py module with configurable limits
- Apply 5 requests/minute limit to login endpoint
- Make rate limit configurable via ORCHARD_LOGIN_RATE_LIMIT env var

Testing:
- Set high rate limit (1000/min) in docker-compose.local.yml for tests
- All 265 tests pass

backend/app/main.py

@@ -1,15 +1,19 @@
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 from fastapi.staticfiles import StaticFiles
 from fastapi.responses import FileResponse
 from contextlib import asynccontextmanager
 import logging
 import os
 
+from slowapi import _rate_limit_exceeded_handler
+from slowapi.errors import RateLimitExceeded
+
 from .config import get_settings
 from .database import init_db, SessionLocal
 from .routes import router
 from .seed import seed_database
 from .auth import create_default_admin
+from .rate_limit import limiter
 
 settings = get_settings()
 logging.basicConfig(level=logging.INFO)
@@ -55,6 +59,10 @@ app = FastAPI(
     lifespan=lifespan,
 )
 
+# Set up rate limiting
+app.state.limiter = limiter
+app.add_exception_handler(RateLimitExceeded, _rate_limit_exceeded_handler)
+
 # Include API routes
 app.include_router(router)
 

backend/app/rate_limit.py

@@ -0,0 +1,16 @@
+"""Rate limiting configuration for Orchard API.
+
+Uses slowapi for rate limiting with IP-based keys.
+"""
+
+import os
+from slowapi import Limiter
+from slowapi.util import get_remote_address
+
+# Rate limiter - uses IP address as key
+limiter = Limiter(key_func=get_remote_address)
+
+# Rate limit strings - configurable via environment for testing
+# Default: 5 login attempts per minute per IP
+# In tests: set ORCHARD_LOGIN_RATE_LIMIT to a high value like "1000/minute"
+LOGIN_RATE_LIMIT = os.environ.get("ORCHARD_LOGIN_RATE_LIMIT", "5/minute")

backend/app/routes.py

@@ -374,9 +374,11 @@ from .auth import (
     check_project_access,
     AuthorizationService,
 )
+from .rate_limit import limiter, LOGIN_RATE_LIMIT
 
 
 @router.post("/api/v1/auth/login", response_model=LoginResponse)
+@limiter.limit(LOGIN_RATE_LIMIT)
 def login(
     login_request: LoginRequest,
     request: Request,

backend/requirements.txt

@@ -10,6 +10,7 @@ pydantic-settings==2.1.0
 python-jose[cryptography]==3.3.0
 passlib[bcrypt]==1.7.4
 bcrypt==4.0.1
+slowapi==0.1.9
 
 # Test dependencies
 pytest>=7.4.0