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/upload-part/route.ts

@@ -0,0 +1,64 @@
+import { NextResponse } from 'next/server';
+import pool from '@/lib/db';
+
+if (!process.env.DISCORD_WEBHOOK_URL) {
+  throw new Error('Please define DISCORD_WEBHOOK_URL in .env.local');
+}
+
+export async function POST(request: Request) {
+  try {
+    const formData = await request.formData();
+    const fileId = formData.get('file_id') as string;
+    const partIndex = formData.get('part_index') as string;
+    const chunk = formData.get('encrypted_chunk') as Blob;
+
+    if (!fileId || !partIndex || !chunk) {
+      return NextResponse.json({ error: 'Missing required form fields' }, { status: 400 });
+    }
+
+    // Forward the chunk to Discord
+    const discordFormData = new FormData();
+    discordFormData.append('file', chunk, `chunk-${partIndex}.bin`);
+    // You can add content to the message if you want
+    // discordFormData.append('content', `File chunk for ${fileId}, part ${partIndex}`);
+
+    const discordRes = await fetch(process.env.DISCORD_WEBHOOK_URL, {
+      method: 'POST',
+      body: discordFormData,
+    });
+
+    if (!discordRes.ok) {
+      const errorBody = await discordRes.json();
+      console.error('Discord API Error:', errorBody);
+      return NextResponse.json({ error: 'Failed to upload to Discord' }, { status: 500 });
+    }
+
+    const discordData = await discordRes.json();
+    const attachment = discordData.attachments[0];
+
+    if (!attachment) {
+        return NextResponse.json({ error: 'No attachment found in Discord response' }, { status: 500 });
+    }
+
+    const discordMessageId = discordData.id;
+    const discordAttachmentUrl = attachment.url;
+    const partSize = attachment.size;
+
+    // Save part metadata to the database
+    const connection = await pool.getConnection();
+    try {
+      await connection.query(
+        'INSERT INTO file_parts (file_id, part_index, discord_message_id, discord_attachment_url, size) VALUES (?, ?, ?, ?, ?)',
+        [fileId, parseInt(partIndex), discordMessageId, discordAttachmentUrl, partSize]
+      );
+    } finally {
+      connection.release();
+    }
+
+    return NextResponse.json({ success: true, part_index: partIndex });
+
+  } catch (error) {
+    console.error('Error uploading part:', error);
+    return NextResponse.json({ error: 'Internal Server Error' }, { status: 500 });
+  }
+}