feat: Implement file upload and management system

- Created database schema for files and file parts.
- Added API endpoint to create a new file and generate an upload token.
- Implemented API endpoint to complete file uploads and generate a download token.
- Developed cron job for cleaning up expired files and deleting associated Discord messages.
- Added API endpoint for soft deletion of files and their parts.
- Implemented API endpoint to fetch file metadata and parts for download.
- Created API endpoint to upload file parts to Discord.
- Developed a client-side download page to handle file decryption and assembly.
- Established database connection pooling for efficient database operations.

src/app/api/cron/cleanup/route.ts

@@ -0,0 +1,59 @@
+import { NextResponse } from 'next/server';
+import pool from '@/lib/db';
+
+if (!process.env.DISCORD_WEBHOOK_URL || !process.env.CRON_SECRET) {
+  throw new Error('Please define DISCORD_WEBHOOK_URL and CRON_SECRET in .env.local');
+}
+
+export async function POST(request: Request) {
+  try {
+    // 1. Authenticate the cron job request
+    const authHeader = request.headers.get('authorization');
+    if (authHeader !== `Bearer ${process.env.CRON_SECRET}`) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+    }
+
+    const connection = await pool.getConnection();
+    try {
+      // 2. Find expired files
+      const [expiredFiles]: any[] = await connection.query(
+        'SELECT id FROM files WHERE expires_at <= NOW() AND deleted = 0'
+      );
+
+      if (expiredFiles.length === 0) {
+        return NextResponse.json({ success: true, message: 'No expired files to clean up.' });
+      }
+
+      let totalCleaned = 0;
+
+      // 3. For each expired file, delete parts and mark as deleted
+      for (const file of expiredFiles) {
+        const file_id = file.id;
+
+        const [partsRows]: any[] = await connection.query(
+          'SELECT discord_message_id FROM file_parts WHERE file_id = ?',
+          [file_id]
+        );
+
+        const deletePromises = partsRows.map(part => {
+          const deleteUrl = `${process.env.DISCORD_WEBHOOK_URL}/messages/${part.discord_message_id}`;
+          return fetch(deleteUrl, { method: 'DELETE' });
+        });
+
+        await Promise.allSettled(deletePromises);
+
+        await connection.query('UPDATE files SET deleted = 1 WHERE id = ?', [file_id]);
+        totalCleaned++;
+      }
+
+      return NextResponse.json({ success: true, message: `Cleaned up ${totalCleaned} expired files.` });
+
+    } finally {
+      connection.release();
+    }
+
+  } catch (error) {
+    console.error('Error during cron cleanup:', error);
+    return NextResponse.json({ error: 'Internal Server Error' }, { status: 500 });
+  }
+}