Make Zotero script comment dynamic and assert valid JS

The generated script's setup comment hardcoded school.second-brain.ru
even though baseUrl is already interpolated elsewhere in the template,
so the comment would lie on any other host. Also add a regression test
that the generated script parses as valid JavaScript, to catch escaping
mistakes in the template literal.

src/lib/clean-pdf/__tests__/zotero-script.test.ts

@@ -9,4 +9,9 @@ describe("buildZoteroScript", () => {
     expect(s).toContain("/api/pdf?url=");
     expect(s).not.toContain("YOUR_KEY");
   });
+
+  it("генерирует синтаксически валидный JS", () => {
+    const s = buildZoteroScript({ apiKey: "sbpdf_test123", baseUrl: "https://school.second-brain.ru" });
+    expect(() => new Function(s)).not.toThrow();
+  });
 });