Tag-based cache invalidation worker

[tayebmokni]

Summary

Implement the invalidation-worker Asynq worker per doc 07 §16.2 that tails the cache_invalidations outbox table. For each row it (1) calls FragmentCache.InvalidateTags, (2) POSTs to the Next.js /api/revalidate webhook, (3) purges Cloudflare cache-tags via API, then (4) deletes the row. Failures are retried with exponential backoff. Crash-safe: if the worker dies mid-run, the row remains and the next invocation picks it up.

Design reference

• docs/07-media-performance.md §16.1, §16.2, §16.3

Acceptance criteria

• Worker tails cache_invalidations rows in order
• For each row: invoke Fragment cache + Next.js webhook + Cloudflare API in sequence
• Row deleted only after all three succeed
• Exponential backoff on transient failures; circuit-breaker on Cloudflare API
• Replay-safe: re-running on a row produces the same invalidation
• Canonical tag vocabulary enforced (post:{uuid}, term:{uuid}, user:{uuid}, type:{slug}, archive:..., media:{uuid}, nav:{uuid}, site:settings, global)
• Tests cover worker restart mid-row and partial failures

Dependencies

#fragment-cache, #isr-webhook

Complexity

M

[tayebmokni]

Closing — shipped in the final-wave PR (#487-#492). Auto-close only fires for first ref.