fix: refactor admin permission checks into util package

[Copilot]

Hardcoded role strings like "chat-admin" and "video-normal-user" were scattered across controllers, routers, and object packages, making role management brittle and difficult to maintain.

Changes

• New util/permission.go with centralized permission functions:

  • IsAdminOrChatAdmin(user) - combines system admin and chat-admin checks
  • IsChatAdmin(user) - chat-admin role check
  • IsVideoNormalUser(user) - video user role check
  • Constants: UserTypeChatAdmin, UserTypeVideoNormalUser

• Replaced inline checks in 5 files:

  • routers/authz_filter.go
  • controllers/util.go, controllers/account.go, controllers/video.go
  • object/util.go

Before:

// Duplicated across codebase
isAdmin := user != nil && (user.IsAdmin || user.Type == "chat-admin")
if user.Type == "video-normal-user" { ... }

After:

// Single source of truth
if !util.IsAdminOrChatAdmin(user) { ... }
if util.IsVideoNormalUser(user) { ... }

All role strings now exist only in util/permission.go.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[feature] refactor out all admin checks like "chat-admin" in backend</issue_title>
<issue_description>Put all permission checking code like user.IsAdmin, user.Type == "chat-admin" into util functions in util package

finally we will not have any static values like "chat-admin" outside of util package</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [feature] refactor out all admin checks like "chat-admin" in backend #2059

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