feat(13-06): TenderDetail renders all cross-source links

Tender.sources[] added to the API client type (sourcePortal, sourceUrl,
sourceNoticeId). TenderDetail now renders one link per TenderSource
with a German portal label (DÖE/tender24/DTVP/...), falling back to
the existing single sourceUrl block when sources is missing or empty
(older responses, single-source tenders).

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

apps/web/src/lib/tender-radar-api.ts

@@ -55,6 +55,18 @@ export interface Tender {
   status: string;
   sourceUrl: string | null;
   publishedAt: string;
+  /**
+   * Cross-source-dedup links (13-06, SCHEMA-03, D-03): all TenderSource
+   * rows for this tender, one per portal it was found on. Optional —
+   * only `getTender` (detail) populates it; `listTenders` rows and
+   * older responses may omit it entirely, so callers must fall back to
+   * the single `sourceUrl` field when it's missing/empty.
+   */
+  sources?: {
+    sourcePortal: string;
+    sourceUrl: string | null;
+    sourceNoticeId: string;
+  }[];
 }
 
 /** Response shape of GET /modules/tender-radar. */