fix(orders): honor skip param in backfill endpoint (was hardcoded to page 1)

The route accepted ?skip=N but always called getList(1, ...) — every
chunk re-processed the FIRST limit orders, leaving offsets > limit
unprocessed. Convert skip to page (floor(skip/limit) + 1) and add a
regression test asserting getList is called with the right page.

src/app/api/v1/orders/backfill-duplicate-checks/route.test.ts

@@ -100,6 +100,26 @@ describe("POST /api/v1/orders/backfill-duplicate-checks", () => {
     expect(body.error).toMatch(/limit/i);
   });
 
+  it("uses the skip param to advance the page (regression: skip was ignored)", async () => {
+    const { getAdminPocketBase } = await import("@/lib/server/pocketbase-admin");
+    const getListSpy = vi.fn().mockResolvedValue({
+      items: [{ id: "x" }],
+      totalItems: 1,
+      page: 5,
+      perPage: 3,
+    });
+    vi.mocked(getAdminPocketBase).mockResolvedValueOnce({
+      autoCancellation: vi.fn(),
+      collection: () => ({ getList: getListSpy }),
+    } as unknown as Awaited<ReturnType<typeof getAdminPocketBase>>);
+
+    const res = await POST(backfillRequest("?limit=2&skip=8"));
+    expect(res.status).toBe(200);
+    // skip=8, limit=2 → page = floor(8/2) + 1 = 5
+    expect(getListSpy).toHaveBeenCalledWith(5, 3, expect.any(Object));
+    expect((await res.json()).nextSkip).toBe(9);
+  });
+
   it("returns 401 when AGENT_API_KEY is missing", async () => {
     delete process.env.AGENT_API_KEY;
     const res = await POST(backfillRequest());

src/app/api/v1/orders/backfill-duplicate-checks/route.ts

@@ -89,10 +89,14 @@ export async function POST(req: NextRequest) {
   const pb = await getAdminPocketBase();
   pb.autoCancellation(false);
 
+  // Convert `skip` to a 1-based page number. PB's getList uses page,
+  // not offset, so we compute `page = floor(skip/limit) + 1`.
+  const page = Math.floor(skip / limit) + 1;
+
   // Fetch `limit + 1` so we can detect whether more rows remain after
   // this chunk without a second `count` query.
   const orders = await pb.collection("orders").getList<{ id: string }>(
-    1,
+    page,
     limit + 1,
     {
       fields: "id",