feat(discover): full reset — clear + rebuild suggestions

POST /api/discover/reset sets discover.resetRequested; the worker, at the
start of the next sweep, clears all PENDING suggestions + contributions +
seed throttles and nulls WatchedArtist.lastDiscoveredAt (keeping
followed/wanted/dismissed decisions), then regenerates everything with current
logic. A 'Reset' button on /discover (2-step confirm) triggers it.

worker 247, web 190 tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

worker/lyra_worker/main.py

@@ -10,7 +10,7 @@ from lyra_worker.claim import claim_next, reclaim_stuck_jobs
 from lyra_worker.config import get_config
 from lyra_worker.crypto import secret_key_problem
 from lyra_worker.db import wait_for_db
-from lyra_worker.discovery import DiscoveryConfig, DiscoveryResult, run_discovery
+from lyra_worker.discovery import DiscoveryConfig, DiscoveryResult, reset_pending, run_discovery
 from lyra_worker.library import clear_staging_root
 from lyra_worker.monitor import MonitorConfig, fulfill_owned_releases, reconcile, sweep
 from lyra_worker.pipeline import run_pipeline
@@ -147,6 +147,10 @@ def maybe_run_discovery(conn, sources, browser, config, dcfg, now, last_discover
 
     starting = not in_progress
     if starting:  # begin a fresh sweep
+        if str(config.get("discover.resetRequested", "")).strip().lower() in _TRUE:
+            reset_pending(conn)  # wipe stale pending suggestions before rebuilding
+            _set_config(conn, "discover.resetRequested", "false")
+            print("worker: discovery reset — cleared pending suggestions, rebuilding", flush=True)
         _set_config(conn, "discover.inProgress", "true")
         _set_config(conn, "discover.requested", "false")