Geo lookup + client info (extract-once) #488

Description

Implement PlatformGeo backed by Fastly SDK. Populate ClientInfo struct from the Fastly request at the entry point and store in RuntimeServices.

Extract-once pattern

ClientInfo is a plain data struct populated once at the entry point — not extracted per-call-site. This eliminates redundant extraction (currently get_client_ip_addr() is called 4+ times in the auction flow alone). Each adapter constructs ClientInfo from its platform request at dispatch time:

• Fastly: req.get_client_ip_addr(), req.get_tls_protocol(), req.get_tls_cipher_openssl_name()
• Cloudflare: CF-Connecting-IP header, cf object TLS fields
• Axum: connection info, X-Forwarded-For header

Call sites to migrate

• geo.rs — req.get_client_ip_addr() for geo lookup → services.client_info.client_ip
• synthetic.rs:71 — req.get_client_ip_addr() for ID generation → services.client_info.client_ip
• didomi.rs:106 — original_req.get_client_ip_addr() for X-Forwarded-For → services.client_info.client_ip
• auction/formats.rs:134 — req.get_client_ip_addr() for DeviceInfo → services.client_info.client_ip
• http_util.rs:134,140 — req.get_tls_protocol() / req.get_tls_cipher_openssl_name() for scheme detection → services.client_info.tls_protocol / services.client_info.tls_cipher

Done when

• ClientInfo populated at entry point
• Geo and client-info reads go through RuntimeServices
• Per-PR gates pass

Blocked by

PR 2

References

• docs/internal/EDGEZERO_MIGRATION.md — Phase 1, PR 7
• Part of EdgeZero Integration #480