feat(crawler): queue-backed manager revalidation fan-out

[bokelley]

Closes #4200 item 2. When a manager rotates its `adagents.json`, every publisher delegating via ads.txt `MANAGERDOMAIN` needs re-validation so its `authorized_agents` view stays in sync. Inline fan-out at managed-network scale (Raptive ≈ 6K publishers) would saturate crawler concurrency, so this PR adds a persistent queue and a bounded worker tick.

What lands

• Migration 471 `manager_revalidation_queue` table mirroring the shape of `catalog_crawl_queue` (367): idempotent insert, `next_attempt_after` for backoff, partial index for the worker's due-row scan, second index on `manager_domain` for ops-side per-manager status.
• `cacheAdagentsManifest` change-detect: reads the previously-cached body before the upsert and compares the contributory subset (`authorized_agents`, `properties`) via recursive stable-key canonicalization. Only actual content drift triggers the fan-out — `$schema` / `last_updated` / trailing-comment noise is intentionally ignored.
• `enqueueManagerRevalidation` walks `publishers WHERE manager_domain = $1` via the partial index added in feat(registry): persist managerdomain discovery provenance on publisher rows #4204, so a Raptive-scale rotation enumerates 6K delegating publishers via an index-only scan. Insert is idempotent and resets attempts/backoff on re-enqueue so a fresh manager change supersedes any in-flight retry window.
• `processManagerRevalidationQueue` worker tick drains up to 50 rows per 5-minute interval at concurrency 10. Success deletes the row; failure advances exponential backoff (1h / 6h / 1d / 3d) and stores `last_error` truncated to 500 chars.

At those bounds, a 6K-publisher manager rotation propagates within ~10 hours — comfortably ahead of the 60-minute organic re-crawl cadence that any single row would catch on its own.

Tests

• Integration (`manager-revalidation-queue.test.ts`): queue idempotency, attempts/backoff reset on re-enqueue, due-row filtering, batch limit, oldest-first ordering, success deletion, geometric backoff (1h → 6h), `last_error` truncation.
• Unit (`manifest-content-changed.test.ts`): null previous, identical manifests, `$schema`/`last_updated` noise ignored, `authorized_agents`/`properties` change detected, order-sensitivity on `authorized_agents`, missing fields treated as empty arrays.

Out of scope

• Item 5 (`/api/registry/managers/:domain/recrawl` endpoint): now possible because the queue + reverse-lookup are in place. Thin wrapper that calls `enqueueManagerRevalidation` and returns the count. Separate PR.
• The `source` enum extension to `adagents_json_via_manager` for per-agent rows in `agent_property_authorizations` (still tracked under AAO crawler/API: persist managerdomain discovery provenance and reverse index #4200 follow-ups).

Refs #4200, #4173, #4204.