webhook: PascalCase payload + ItemAdded only, switch ✓✓ signal to ffprobe

monitoring the mqtt broker revealed two bugs and one design dead-end:

1. the jellyfin-plugin-webhook publishes pascalcase fields
   (NotificationType, ItemId, ItemType) and we were reading camelcase
   (event, itemId, itemType). every real payload was rejected by the
   first guard — the mqtt path never ingested anything.

2. the plugin has no ItemUpdated / Library.* notifications. file
   rewrites on existing items produce zero broker traffic (observed:
   transcode + manual refresh metadata + 'recently added' appearance
   → no mqtt messages). ✓✓ via webhook is structurally impossible.

fix the webhook path so brand-new library items actually get ingested,
and narrow ACCEPTED_EVENTS to just 'ItemAdded' (the only library-side
event the plugin emits).

move the ✓✓ signal from webhook-corroboration to post-execute ffprobe
via the existing verifyDesiredState helper: after ffmpeg returns 0 we
probe the output file ourselves and flip verified=1 on match. the
preflight-skipped path sets verified=1 too. renamed the db column
webhook_verified → verified (via idempotent RENAME COLUMN migration)
since the signal is no longer webhook-sourced, and updated the Done
column tooltip to reflect that ffprobe is doing the verification.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/db/index.ts

@@ -74,6 +74,10 @@ function migrate(db: Database): void {
 		}
 	};
 	alter("ALTER TABLE review_plans ADD COLUMN webhook_verified INTEGER NOT NULL DEFAULT 0");
+	// 2026-04-14: renamed webhook_verified → verified once we realized the
+	// signal would come from our own ffprobe, not from a Jellyfin webhook.
+	// RENAME COLUMN preserves values; both alters are no-ops on fresh DBs.
+	alter("ALTER TABLE review_plans RENAME COLUMN webhook_verified TO verified");
 }
 
 function seedDefaults(db: Database): void {