feat(web-ui): expose citation-corroboration badge on halachot (X11)

- db.list_halachot: aggregate corroboration_count (distinct positive sources)
  + corroboration_negative from halacha_citation_corroboration (LEFT JOIN)
- web-ui: CorroborationBadge — 'מתוקף · N ציטוטים' at ≥2 (gold), soft single
  citation, danger badge on negative treatment; native title tooltips
- shown in ExtractedHalachotSection (per-precedent) + halacha review panel

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

web-ui/src/lib/api/precedent-library.ts

@@ -83,6 +83,11 @@ export type Halacha = {
   court?: string;
   decision_date?: string | null;
   precedent_level?: string;
+  /* X11 citation corroboration — how many distinct later courts/committees
+   * adopted this halacha (positive treatment), and whether any cited it
+   * negatively (distinguished/criticized/overruled). */
+  corroboration_count?: number;
+  corroboration_negative?: boolean;
 };
 
 export type RelatedCase = {