Refactor Dockerfile for improved build process; switch to node:20 base image, add build step, and configure volume and port exposure. Update package dependencies for bcrypt and bcryptjs, remove unused files, and enhance README with clearer project structure and setup instructions.

src/app/api/admin/password/route.ts

@@ -1,7 +1,7 @@
 import { NextResponse } from 'next/server';
 import fs from 'fs';
 import path from 'path';
-import bcrypt from 'bcrypt';
+import bcrypt from 'bcryptjs';
 
 const adminPath = path.join(process.cwd(), 'posts', 'admin.json');
 const tempPath = path.join(process.cwd(), 'posts', 'admin.json.tmp');