fix: reject blank imported budget item names

src/export/json.test.ts

@@ -163,6 +163,23 @@ describe("import rejects invalid folder graph", () => {
     data.posts[0]!.order = 0;
     expect(() => parse(data)).toThrow(ImportValidationError);
   });
+
+  test("rejects a blank post name", () => {
+    const data = populated();
+    data.posts[0]!.name = "  ";
+    expect(() => parse(data)).toThrow(ImportValidationError);
+  });
+
+  test("rejects a blank recurring-cost name", () => {
+    const data = populated();
+    data.recurring.push({
+      id: "rent", name: "  ", order: 3, folderId: null, archived: false,
+      amount: { amount: 100, currency: "DKK" }, startDate: "2026-01",
+      recurrence: { kind: "everyNMonths", n: 1 }, anchoring: "calendar",
+      splitMode: "percent", splits: [{ postId: data.posts[0]!.id, value: 100, absorbsRemainder: true }],
+    });
+    expect(() => parse(data)).toThrow(ImportValidationError);
+  });
 });
 
 test("describeDataset counts what an import would replace", () => {

src/export/json.ts

@@ -190,9 +190,15 @@ function requireFolderTree(data: Dataset): void {
     requireLocation(folder.parentId, folder.order, `Folder "${folder.id}"`);
   }
   for (const post of data.posts) {
+    if (typeof post?.name !== "string" || !post.name.trim()) {
+      throw new ImportValidationError("Post has an empty name");
+    }
     requireLocation(post?.folderId, post?.order, `Post "${post?.name}"`);
   }
   for (const cost of data.recurring) {
+    if (typeof cost?.name !== "string" || !cost.name.trim()) {
+      throw new ImportValidationError("Recurring cost has an empty name");
+    }
     requireLocation(cost?.folderId, cost?.order, `Recurring cost "${cost?.name}"`);
   }
 }