feat(interests): CM-2 Part B — deal-price override route + UI on linked berths

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

src/app/api/v1/interests/[id]/berths/[berthId]/price/handlers.ts

@@ -0,0 +1,39 @@
+/**
+ * Route handler for `/api/v1/interests/[id]/berths/[berthId]/price` (CM-2 Part B).
+ *
+ * Sets or clears the deal-specific price override for one (interest, berth).
+ * In handlers.ts so integration tests can call it directly.
+ */
+
+import { NextResponse } from 'next/server';
+import { z } from 'zod';
+
+import { type RouteHandler } from '@/lib/api/helpers';
+import { parseBody } from '@/lib/api/route-helpers';
+import { errorResponse } from '@/lib/errors';
+import { setBerthPriceOverride } from '@/lib/services/interest-berths.service';
+
+const bodySchema = z.object({
+  price: z.number().nonnegative().nullable(),
+  currency: z.string().min(1).max(8).optional(),
+});
+
+export const putHandler: RouteHandler<{ id: string; berthId: string }> = async (
+  req,
+  ctx,
+  params,
+) => {
+  try {
+    const body = await parseBody(req, bodySchema);
+    await setBerthPriceOverride(
+      params.id!,
+      params.berthId!,
+      body.price,
+      body.currency ?? null,
+      ctx.portId,
+    );
+    return new NextResponse(null, { status: 204 });
+  } catch (error) {
+    return errorResponse(error);
+  }
+};

src/app/api/v1/interests/[id]/berths/[berthId]/price/route.ts

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+import { withAuth, withPermission } from '@/lib/api/helpers';
+
+import { putHandler } from './handlers';
+
+export const PUT = withAuth(withPermission('interests', 'edit', putHandler));