feat(berths): split Documents tab into Spec + Deal Documents

Berth detail page now has two tabs:
  - Spec: the existing versioned berth-spec PDF surface (current panel,
    version history, parser badge).
  - Deal Documents: NEW. Lists EOIs / contracts / etc. attached to
    interests currently linked to this berth via interest_berths.

New service helper listDealDocumentsForBerth joins documents →
interests → interest_berths with a port_id guard on both sides.
GET /api/v1/berths/[id]/deal-documents wraps it, gated on berths.view.

Read-only — title, type, status badge, and an Open link to the source
interest page. Edits / sends still happen on the interest's own page.
The Spec tab paragraph now points reps to the new Deal Documents tab
instead of telling them to navigate via Interests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/api/v1/berths/[id]/deal-documents/route.ts

@@ -0,0 +1,24 @@
+import { NextResponse } from 'next/server';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { errorResponse, NotFoundError } from '@/lib/errors';
+import { listDealDocumentsForBerth } from '@/lib/services/documents.service';
+
+/**
+ * GET /api/v1/berths/[id]/deal-documents
+ *
+ * Lists documents attached to interests currently linked to this berth.
+ * Same permission gate as the berth page itself (berths.view).
+ */
+export const GET = withAuth(
+  withPermission('berths', 'view', async (_req, ctx, params) => {
+    try {
+      const berthId = params.id;
+      if (!berthId) throw new NotFoundError('Berth');
+      const data = await listDealDocumentsForBerth(ctx.portId, berthId);
+      return NextResponse.json({ data });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);