Thread RuntimeServices into integration and provider entry points

[aram356]

Description

Pure signature-change PR that adds &RuntimeServices to integration and provider entry points without changing any types. This splits the "RuntimeServices plumbing" concern out of the integration type migration PR (PR 13), halving its scope.

Fastly types remain in place — this compiles independently because adding a parameter to trait methods + implementations is a mechanical change that the compiler enforces.

Signature changes

• IntegrationProxy::handle(&self, settings, req) → handle(&self, settings, services: &RuntimeServices, req)
• IntegrationRegistry::handle_proxy(method, path, settings, req) → handle_proxy(method, path, settings, services: &RuntimeServices, req)
• AuctionContext struct — add pub services: &'a RuntimeServices field

Files touched

• Framework: registry.rs, auction/provider.rs, auction/types.rs
• Callers: auction/orchestrator.rs, adapter main.rs
• All 8 proxy integration modules + 2 test impls in registry.rs
• All 3 auction provider implementations (prebid.rs, aps.rs, adserver_mock.rs)

What this PR does NOT do

• No type changes (fastly::Request/Response stay)
• No send()/send_async() migration
• No behavior changes — implementations accept services but don't use it yet

Done when

• All integration + provider traits accept &RuntimeServices
• All callers thread RuntimeServices through
• No Fastly type changes
• Per-PR gates pass

Blocked by

PR 12

References

• docs/internal/EDGEZERO_MIGRATION.md — Phase 2, PR 12.5
• Part of EdgeZero migration #480