feat: initial Greasy Sprocket website — Astro static + Go feedback service

- Astro 5.x static site with content collections for extensions
- Pages: index, [slug] (per-extension), coffee (Ko-fi), feedback form
- Go binary gs-feedback: SQLite storage + Discord webhook notification
- Nginx config: static serving + POST proxy to Go backend
- Deploy script: build + rsync to VPS
- ThockBoard landing page with features and sound pack listing

astro/astro.config.mjs

@@ -0,0 +1,10 @@
+import { defineConfig } from 'astro/config';
+
+export default defineConfig({
+  site: 'https://greasysprocket.com',
+  output: 'static',
+  server: {
+    host: '127.0.0.1',
+    port: 4321,
+  },
+});