style(backend): remove unused imports

app/services/student_picture_service.py

@@ -1,18 +1,4 @@
 import os
-import random
-import string
-from datetime import datetime, timedelta
-
-from snowflake import SnowflakeGenerator
-
-from app.globals import Globals
-from app.models.Student import Student
-from app.services.mail_service import MailService
-from app.services.redis_service import RedisService
-from app.tools.jwt_engine import generate_jwt
-from app.tools.password_tools import hash_password
-from app.tools.teklogger import log_debug, log_warning
-
 
 class StudentPictureService:
     @staticmethod