feat(backend): implement pricing engine for loyalty points and 3-level promotions

apps/backend/src/routes/promotions.ts

@@ -0,0 +1,20 @@
+import { Elysia, t } from "elysia";
+import prisma from "../lib/prisma";
+
+export const promotionsRoute = new Elysia({ prefix: "/promotions" })
+  .get("/active", async () => {
+    const now = new Date()
+    return await prisma.promotion.findMany({
+      where: {
+        isActive: true,
+        OR: [
+          { startDate: null },
+          { startDate: { lte: now } }
+        ],
+        AND: [
+          { OR: [{ endDate: null }, { endDate: { gte: now } }] }
+        ]
+      },
+      orderBy: { level: 'asc' }
+    });
+  });