feat: add build hash to sidebar footer and Gitea CI/CD deploy workflow

- Inject git commit short hash at build time via NEXT_PUBLIC_BUILD_HASH
- Display build hash in sidebar footer for version tracking
- Add Gitea Actions workflow to auto-deploy on push to master (SSH → pull → rebuild)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

next.config.ts

@@ -1,8 +1,20 @@
 import type { NextConfig } from "next";
+import { execSync } from "child_process";
+
+const commitHash = (() => {
+  try {
+    return execSync("git rev-parse --short HEAD").toString().trim();
+  } catch {
+    return "dev";
+  }
+})();
 
 const nextConfig: NextConfig = {
   output: "standalone",
   serverExternalPackages: ["pdf-parse", "drizzle-orm", "pg"],
+  env: {
+    NEXT_PUBLIC_BUILD_HASH: commitHash,
+  },
 };
 
 export default nextConfig;