Open buy buttons in CrowdRepublic crowdfunding modal.

Replace donate.stream links with a modal announcing the upcoming campaign on CrowdRepublic, with RU/EN copy and the old buy URL commented out.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/siteContent.test.ts

@@ -2,6 +2,7 @@ import assert from "node:assert/strict";
 import { describe, it } from "node:test";
 
 import {
+  CROWDFUNDING_URL,
   DOWNLOAD_ARTIFACTS,
   DOWNLOAD_LINKS,
   FAQ_IDS,
@@ -68,9 +69,9 @@ describe("siteContent", () => {
     );
   });
 
-  it("wires download anchor and external buy link", () => {
+  it("wires download anchor and CrowdRepublic crowdfunding url", () => {
     assert.equal(SITE_LINKS.download, "#platforms");
-    assert.equal(SITE_LINKS.buy, "https://donate.stream/ttrpgplayer");
+    assert.equal(CROWDFUNDING_URL, "https://crowdrepublic.ru/");
   });
 
   it("maps each feature variant to a screenshot asset", () => {