fix: rate-limit and audit by real client address

uvicorn does not trust forwarded headers from a peer outside
forwarded_allow_ips, so request.client.host was the web gateway for every
request. The auth-source bucket therefore counted all customers together:
60 failed logins from one attacker locked out everyone. Security events
recorded the gateway address, which made the audit trail useless for
attribution.

The gateway now overwrites X-Forwarded-For with the peer address it observed
instead of appending to whatever the client sent, so the header carries one
value the client cannot choose, and client_ip() resolves it with a fallback to
the connection peer.

The guest-session limiter was keyed on the environment name, making it one
global bucket of 120 per 15 minutes: roughly eight new visitors a minute for
the whole site before legitimate traffic started receiving 429. It is now per
source, and the ceiling is deliberately generous because offices and mobile
carriers put many real customers behind a single address.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

local/app.py

@@ -17,7 +17,7 @@ from . import db
 from .adapters import FakeFreight, FakePayment, LocalS3Storage, require_runtime
 from .models import Freight, Move, Pay, QuoteRequest, Review, UploadStart, OperatorLogin
 from .pricing import price
-from .auth import COOKIE_SECURE, owner, session_row, new_session, operator, throttle, audit, rate_limit
+from .auth import COOKIE_SECURE, client_ip, owner, session_row, new_session, operator, throttle, audit, rate_limit
 from .scanning import require_clean
 
 require_runtime()
@@ -28,6 +28,10 @@ ENVIRONMENT = os.environ.get('APP_ENV', 'local')
 PUBLIC_ORIGIN = os.environ.get('PUBLIC_ORIGIN', 'http://localhost')
 ALLOWED_HOSTS = [host for host in os.environ.get('ALLOWED_HOSTS', 'localhost,127.0.0.1').split(',') if host]
 ALLOWED_ORIGINS = [origin for origin in os.environ.get('ALLOWED_ORIGINS', PUBLIC_ORIGIN).split(',') if origin]
+# Per source and generous: a browser needs one session and keeps the cookie, but
+# offices and mobile carriers put many real customers behind one address, so a
+# tight per-IP ceiling would lock out the same people the old global one did.
+GUEST_SESSION_LIMIT = int(os.environ.get('GUEST_SESSION_LIMIT', '240'))
 PART_BYTES = int(os.environ.get('UPLOAD_PART_BYTES', '8388608'))
 if not 5242880 <= PART_BYTES <= 67108864:
     raise RuntimeError('UPLOAD_PART_BYTES must be between 5 and 64 MiB')
@@ -56,7 +60,7 @@ def operator_login(body: OperatorLogin, request: Request, response: Response):
     valid_user = secrets.compare_digest(email.encode(), configured_email.encode())
     valid_password = secrets.compare_digest(body.password.encode(), os.environ['OPERATOR_PASSWORD'].encode())
     if not (valid_user and valid_password):
-        audit('operator_login_failed')
+        audit('operator_login_failed', ip=client_ip(request))
         raise HTTPException(401, 'Invalid operator login')
     token = secrets.token_urlsafe(32)
     with db.connect() as c:
@@ -84,11 +88,11 @@ async def safe_headers(request, call_next):
     if request.method not in ('GET','HEAD','OPTIONS'):
         origin = request.headers.get('origin')
         if request.headers.get('sec-fetch-site') == 'cross-site' or (origin and origin not in ALLOWED_ORIGINS):
-            audit('cross_origin_rejected')
+            audit('cross_origin_rejected', ip=client_ip(request))
             return JSONResponse({'detail':'Cross-origin request rejected'}, status_code=403)
     response = await call_next(request)
     if response.status_code in (401,403,429) or response.status_code>=500:
-        audit('http_security_event', method=request.method, status=response.status_code)
+        audit('http_security_event', method=request.method, status=response.status_code, ip=client_ip(request))
     response.headers['Cache-Control'] = 'no-store'
     response.headers['X-Content-Type-Options'] = 'nosniff'
     response.headers['Referrer-Policy'] = 'no-referrer'
@@ -111,7 +115,9 @@ def session(request: Request, response: Response):
     try:
         session_id = owner(request)
     except HTTPException:
-        rate_limit('guest-sessions', ENVIRONMENT, 120, 900)
+        # Per source, not per deployment: keyed on the environment name this was a
+        # single global bucket, so ~8 new visitors a minute exhausted it site-wide.
+        rate_limit('guest-sessions', client_ip(request), GUEST_SESSION_LIMIT, 900)
         with db.connect() as c:
             session_id = new_session(c, response)
     return {'environment': ENVIRONMENT, 'cart_scope': str(session_id), 'part_bytes': PART_BYTES,