Implement config-first generic OpenRTB auction providers

[ChristianPavilonis]

Context

PR #1016 defines the approved config-first auction-provider architecture. This issue tracks the follow-up implementation and production rollout work described by that design.

Scope

• Replace singleton PBS/APS auction wiring with a shared, compiled auction plan.
• Support map-shaped [auction.providers.<id>] and [auction.bidders.<id>] configuration.
• Add generic OpenRTB execution with typed Standard, Prebid Server, and APS profiles.
• Preserve PBS/APS request, response, signing, routing, mediation, telemetry, and browser behavior parity.
• Validate provider endpoints, backend names, target capabilities, collisions, signing, mediation, and profile configuration at startup.
• Keep adserver_mock mediation static and preserve provider ID, returned seat, and browser delivery bidder identity as separate concepts.
• Update adapters, CLI overlays, examples, fixtures, documentation, and integration tests.

Acceptance criteria

• Public configuration is map-shaped; the former providers: Vec<String> shape is rejected.
• All adapters compile and share one validated Arc<AuctionPlan>.
• Disabled, zero-provider, and all-skipped auctions complete safely without provider I/O.
• PBS and APS parity tests and OpenRTB golden tests pass.
• Browser Prebid demand is restricted to authoritative configured server bidders.
• Logical auction budgets remain distinct from adapter transport timeout canonicalization.
• Redirects are refused and no second request is sent.
• Rust, adapter, CLI, integration, JS, formatting, docs, and clippy verification gates pass.
• Target-aware config-push validation runs before remote config I/O once the EdgeZero callback dependency is published and pinned.

Dependency / blocker

The target-aware pre-write config-push callback is implemented locally in EdgeZero at commit e3259483636969f6f17a2a55daaf2cf8059b7978, but that commit is not currently resolvable from a remote branch. Keep EdgeZero dependencies on the v0.0.4 lineage until the callback can be pinned atomically.

Related

• Design PR: Spec: auction provider refactor #1016