feat(interests): CM-2 Part B — interest_berths price override (data + resolver)

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

src/lib/services/interest-berths.service.ts

@@ -170,6 +170,8 @@ export async function listBerthsForInterest(
       addedBy: interestBerths.addedBy,
       addedAt: interestBerths.addedAt,
       notes: interestBerths.notes,
+      priceOverride: interestBerths.priceOverride,
+      priceOverrideCurrency: interestBerths.priceOverrideCurrency,
       mooringNumber: berths.mooringNumber,
       area: berths.area,
       status: berths.status,
@@ -444,3 +446,49 @@ export async function removeInterestBerth(
     .delete(interestBerths)
     .where(and(eq(interestBerths.interestId, interestId), eq(interestBerths.berthId, berthId)));
 }
+
+// ─── Per-interest price override (CM-2 Part B) ───────────────────────────────
+
+/**
+ * Resolve the effective price for a berth in the context of an interest. The
+ * deal-specific override (when set) supersedes the berth's canonical list
+ * price; the override carries its own currency, falling back to the base
+ * currency when null. Pure — safe to unit-test without a DB.
+ */
+export function resolveBerthPriceForInterest(
+  override: { priceOverride: string | null; priceOverrideCurrency: string | null },
+  base: { price: string | null; priceCurrency: string },
+): { price: string | null; currency: string } {
+  if (override.priceOverride != null) {
+    return {
+      price: override.priceOverride,
+      currency: override.priceOverrideCurrency ?? base.priceCurrency,
+    };
+  }
+  return { price: base.price, currency: base.priceCurrency };
+}
+
+/**
+ * Set (or clear, when `price` is null) the deal-specific price for one
+ * (interest, berth). Tenant-scoped: the interest must belong to `portId`.
+ * Does not touch `berths.price`.
+ */
+export async function setBerthPriceOverride(
+  interestId: string,
+  berthId: string,
+  price: number | null,
+  currency: string | null,
+  portId: string,
+): Promise<void> {
+  const interestRow = await db.query.interests.findFirst({
+    where: and(eq(interests.id, interestId), eq(interests.portId, portId)),
+  });
+  if (!interestRow) throw new NotFoundError('Interest');
+  await db
+    .update(interestBerths)
+    .set({
+      priceOverride: price == null ? null : String(price),
+      priceOverrideCurrency: price == null ? null : (currency ?? 'USD'),
+    })
+    .where(and(eq(interestBerths.interestId, interestId), eq(interestBerths.berthId, berthId)));
+}