Fix backend TypeScript build errors

- Inline tsconfig.base.json settings into backend/tsconfig.json so the
  Docker build (which only copies backend/) can resolve them
- Replace default imports of Node built-ins (crypto, net) with named imports
- Replace default bcrypt import with named imports (compare, hash)
- Switch @fastify/websocket from v8 to v7 (SocketStream API) to match
  Fastify v4 peer dependency; update WebSocket handler signatures accordingly
- Remove obsolete `version` key from docker-compose.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/utils/encryption.ts

@@ -1,17 +1,16 @@
-import crypto from 'crypto';
+import { createCipheriv, createDecipheriv, createHash, randomBytes } from 'crypto';
 
 const ALGORITHM = 'aes-256-cbc';
 const IV_LENGTH = 16;
 
 function getKey(): Buffer {
   const raw = process.env.ENCRYPTION_KEY || '';
-  // Derive exactly 32 bytes from whatever key string is provided
-  return crypto.createHash('sha256').update(raw).digest();
+  return createHash('sha256').update(raw).digest();
 }
 
 export function encrypt(text: string): string {
-  const iv = crypto.randomBytes(IV_LENGTH);
-  const cipher = crypto.createCipheriv(ALGORITHM, getKey(), iv);
+  const iv = randomBytes(IV_LENGTH);
+  const cipher = createCipheriv(ALGORITHM, getKey(), iv);
   const encrypted = Buffer.concat([cipher.update(text, 'utf8'), cipher.final()]);
   return `${iv.toString('hex')}:${encrypted.toString('hex')}`;
 }
@@ -20,7 +19,7 @@ export function decrypt(encryptedText: string): string {
   const [ivHex, encryptedHex] = encryptedText.split(':');
   const iv = Buffer.from(ivHex, 'hex');
   const encrypted = Buffer.from(encryptedHex, 'hex');
-  const decipher = crypto.createDecipheriv(ALGORITHM, getKey(), iv);
+  const decipher = createDecipheriv(ALGORITHM, getKey(), iv);
   const decrypted = Buffer.concat([decipher.update(encrypted), decipher.final()]);
   return decrypted.toString('utf8');
 }