feat(goldset): separate court rulings from committee decisions in tagging

Tagging is easier one source-type at a time. goldset_list now returns
case_law.source_type; the page adds:
- a filter (הכל / פסקי דין / ועדת ערר) with live counts,
- a group-sort so even in "הכל" all court rulings come first, then all
  committee decisions,
- a per-card source badge (פסק-דין / ועדת ערר).

Verified: tsc --noEmit 0; source_type splits the live batch 58 court / 92 committee.

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

web-ui/src/lib/api/goldset.ts

@@ -28,6 +28,7 @@ export type GoldsetItem = {
   review_status: string;
   case_number: string | null;
   case_name: string | null;
+  source_type: string | null;  // 'court_ruling' | 'appeals_committee' | ''
 };
 
 export type GoldsetScore = {