Changed user logic to display name and refined requirements page design

backend/src/main.py

@@ -314,6 +314,20 @@ def _require_role(user, allowed_role_ids: List[int], action: str = "perform this
         )
 
 
+def _get_display_name(user) -> str:
+    """
+    Get the best display name for a user.
+    Falls back in order: full_name -> username -> sub.
+    
+    Args:
+        user: The database user object
+        
+    Returns:
+        The best available display name for the user
+    """
+    return user.full_name or user.username or user.sub
+
+
 async def _verify_project_membership(project_id: int, user_id: int, db: AsyncSession):
     """Helper to verify user is a member of a project."""
     project_repo = ProjectRepository(db)
@@ -570,7 +584,7 @@ async def get_project_members(
     return [
         ProjectMemberResponse(
             id=member.id,
-            sub=member.sub,
+            sub=_get_display_name(member),
             role_id=member.role_id,
             role_name=member.role.role_name if member.role else "unknown",
             role_display_name=ROLE_DISPLAY_NAMES.get(member.role.role_name, member.role.role_name.title()) if member.role else "Unknown",
@@ -647,7 +661,7 @@ async def update_member_role(
     
     return ProjectMemberResponse(
         id=updated_user.id,
-        sub=updated_user.sub,
+        sub=_get_display_name(updated_user),
         role_id=updated_user.role_id,
         role_name=role.role_name,
         role_display_name=ROLE_DISPLAY_NAMES.get(role.role_name, role.role_name.title()),
@@ -772,9 +786,9 @@ def _build_requirement_response(req) -> RequirementResponse:
         # Get the latest validation
         latest_validation = max(req.validations, key=lambda v: v.created_at or req.created_at)
         validation_status = latest_validation.status.status_name if latest_validation.status else "Not Validated"
-        # Try to get username from user relationship
+        # Try to get display name from user relationship
         if latest_validation.user:
-            validated_by = latest_validation.user.sub
+            validated_by = _get_display_name(latest_validation.user)
         validated_at = latest_validation.created_at
         validation_version = latest_validation.req_version_snapshot
     
@@ -1112,7 +1126,7 @@ async def create_validation(
         req_version_snapshot=validation.req_version_snapshot,
         comment=validation.comment,
         created_at=validation.created_at,
-        validator_username=user.sub,
+        validator_username=_get_display_name(user),
         validator_id=user.id
     )
 
@@ -1159,7 +1173,7 @@ async def get_validation_history(
             req_version_snapshot=v.req_version_snapshot,
             comment=v.comment,
             created_at=v.created_at,
-            validator_username=v.user.sub,
+            validator_username=_get_display_name(v.user),
             validator_id=v.user_id
         )
         for v in validations
@@ -1416,7 +1430,7 @@ async def create_requirement_link(
             "req_name": target_req.req_name,
             "tag_code": target_req.tag.tag_code
         },
-        created_by_username=user.sub,
+        created_by_username=_get_display_name(user),
         created_by_id=user.id,
         created_at=link.created_at
     )