chore: migrate from Gitea to GitHub

Replace Gitea CI workflow with GitHub Actions workflow using gh CLI
for release creation. Update auto-updater, changelog fetch, download
links, electron-builder publish config, and package.json homepage to
point at github.com/bigjakk/Krunker-Civilian-Client.

src/main/index.ts

@@ -683,7 +683,7 @@ async function launchApp(): Promise<void> {
     const tag = version.startsWith('v') ? version : `v${version}`;
     try {
       const data = await new Promise<string>((resolve, reject) => {
-        httpsGet(`https://gitea.crjlab.net/api/v1/repos/bigjakk/Krunker-Civilian-Client/releases/tags/${tag}`, (res) => {
+        httpsGet(`https://api.github.com/repos/bigjakk/Krunker-Civilian-Client/releases/tags/${tag}`, { headers: { 'User-Agent': 'KCC' } }, (res) => {
           let body = '';
           res.on('data', (chunk: string) => { body += chunk; });
           res.on('end', () => resolve(body));

src/main/updater.ts

@@ -13,11 +13,9 @@ export interface UpdateInfo {
 export type ProgressCallback = (percent: number) => void;
 
 const UPDATE_CONFIG = {
-  // Gitea provider
-  checkUrl: 'https://gitea.crjlab.net/api/v1/repos/bigjakk/Krunker-Civilian-Client/releases/latest',
+  checkUrl: 'https://api.github.com/repos/bigjakk/Krunker-Civilian-Client/releases/latest',
   assetPattern: /Setup\.exe$/i,
-  // Allowed hosts for update check and download (including redirects)
-  allowedHosts: ['gitea.crjlab.net'],
+  allowedHosts: ['github.com', 'api.github.com', 'objects.githubusercontent.com'],
 };
 
 const CHECK_TIMEOUT_MS = 10000;