chore(site): point astro site at gettechapi.github.io after org transfer

Repo moved Seungpyo1007/TechAPI -> GetTechAPI/TechAPI, so the Pages origin is
now gettechapi.github.io. base (/TechAPI) is unchanged since the repo name is
the same. Fixes canonical/sitemap absolute URLs (page loads were already fine
because asset paths use BASE_URL).

Author: Seungpyo1007

site/astro.config.mjs

@@ -3,6 +3,6 @@ import { defineConfig } from 'astro/config';
 // GitHub Pages project site. Data dump (v1/, openapi.json) is copied alongside
 // the built site in CI, so internal links use import.meta.env.BASE_URL.
 export default defineConfig({
-  site: 'https://seungpyo1007.github.io',
+  site: 'https://gettechapi.github.io',
   base: '/TechAPI',
 });