Added 3 new tests for A06 proxy chain verification:
1. test_rate_limit_independent_limits_for_two_clients_through_proxy
- Two clients behind trusted proxy have independent rate limits
- Client 1 blocked after 5 requests, Client 2 still allowed
2. test_forged_xff_rejected_on_untrusted_port
- XFF from untrusted connection is ignored
- Real client IP used for rate limiting, not forged XFF
3. test_direct_access_without_xff_header
- Direct access without XFF uses real client IP
- Hash is of real IP, not empty string
Verification:
- 8/8 rate limit tests pass
- Docker network CIDR (172.17.0.0/16) tested
- Forged XFF properly rejected from untrusted sources
- Independent rate limits verified for multiple clients
- Add _is_trusted_proxy() to check client IP against trusted CIDRs
- Only use X-Forwarded-For if connection came from trusted proxy
- Add TRUSTED_PROXY_CIDRS config (default: 127.0.0.1/32, ::1/128)
- Add parse_comma_separated_lists for env var parsing
- Add 3 unit tests: trusted CIDR check, untrusted ignores forwarded, trusted uses forwarded
ik