Fix FinTS transaction deduplication

convex/transactions.test.ts

@@ -186,4 +186,76 @@ describe("transactions.list", () => {
     expect(effectiveResult.page.map((tx) => tx._id)).toEqual([seeded.shiftedId]);
     expect(bookingResult.page).toEqual([]);
   });
+
+  test("orders effective month results by booking date instead of import creation time", async () => {
+    const t = convexTest(schema, modules);
+
+    const seeded = await t.run(async (ctx) => {
+      const userId = await ctx.db.insert("users", {
+        name: "Ordering User",
+        email: "ordering@example.com",
+      });
+      const accountId = await ctx.db.insert("accounts", {
+        userId,
+        name: "Girokonto",
+        type: "checking",
+        openingBalance: 0,
+        currency: "EUR",
+        isArchived: false,
+      });
+
+      const olderCreatedNewestBookingId = await ctx.db.insert("transactions", {
+        userId,
+        accountId,
+        bookingDate: "2026-06-23",
+        description: "Newest booking created first",
+        amount: -10,
+        isPending: false,
+        effectiveMonth: "2026-06",
+      });
+      const newerCreatedOldestBookingId = await ctx.db.insert("transactions", {
+        userId,
+        accountId,
+        bookingDate: "2026-06-15",
+        description: "Oldest booking created later",
+        amount: -20,
+        isPending: false,
+        effectiveMonth: "2026-06",
+      });
+      const middleBookingId = await ctx.db.insert("transactions", {
+        userId,
+        accountId,
+        bookingDate: "2026-06-22",
+        description: "Middle booking created last",
+        amount: -30,
+        isPending: false,
+        effectiveMonth: "2026-06",
+      });
+
+      return {
+        userId,
+        olderCreatedNewestBookingId,
+        newerCreatedOldestBookingId,
+        middleBookingId,
+      };
+    });
+
+    const asUser = t.withIdentity({
+      subject: `${seeded.userId}|test-session`,
+      tokenIdentifier: `test:${seeded.userId}`,
+    });
+
+    const result = await asUser.query(api.transactions.list, {
+      paginationOpts: { cursor: null, numItems: 20 },
+      from: "2026-06-01",
+      to: "2026-06-30",
+      basis: "effective",
+    });
+
+    expect(result.page.map((tx) => tx._id)).toEqual([
+      seeded.olderCreatedNewestBookingId,
+      seeded.middleBookingId,
+      seeded.newerCreatedOldestBookingId,
+    ]);
+  });
 });