Fix backend bugs: password hash column rename, dynamic import, AuditLog response_model, websocket reference, missing exports, bcrypt version pin

backend/app/routers/auth.py

@@ -4,6 +4,8 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select
 from typing import Optional
 
+from datetime import datetime
+
 from app.core.database import get_db
 from app.core.security import (
     verify_password,
@@ -33,7 +35,7 @@ async def login(request: LoginRequest, db: AsyncSession = Depends(get_db)):
     result = await db.execute(stmt)
     user = result.scalar_one_or_none()
     
-    if not user or not verify_password(request.password, user.password_sha512):
+    if not user or not verify_password(request.password, user.password_hash):
         raise HTTPException(
             status_code=status.HTTP_401_UNAUTHORIZED,
             detail="Invalid username or password",
@@ -120,7 +122,7 @@ async def register(request: UserCreate, db: AsyncSession = Depends(get_db)):
     # Create new user
     new_user = User(
         username=request.username,
-        password_sha512=hash_password(request.password),
+        password_hash=hash_password(request.password),
         salt="random_salt",  # In production, generate random salt
         email=request.email,
         country=request.country,