feat(ST-l9kkxh2m): /reset-password pagina + resetPasswordAction + hashPassword

- lib/auth.ts: hashPassword(password) geëxporteerd (bcrypt, rounds=12)
- actions/auth.ts: resetPasswordAction met Zod-validatie (min 8, superRefine gelijkheid),
  prisma.user.update (password_hash + must_reset_password=false), redirect /dashboard
- app/(auth)/reset-password/page.tsx: server guard (userId check + must_reset_password check)
- app/(auth)/reset-password/reset-form.tsx: client form (nieuw wachtwoord + bevestiging)
- __tests__/actions/auth.test.ts: 3 tests voor resetPasswordAction

lib/auth.ts

@@ -66,3 +66,7 @@ export async function verifyUser(username: string, password: string) {
 
   return user
 }
+
+export async function hashPassword(password: string): Promise<string> {
+  return bcrypt.hash(password, 12)
+}