Hide frozen field from non-admin users in API responses

[Copilot]

The Frozen field on holes was being exposed to all users. This admin-only field should only be visible to administrators.

Changes

• Model: Changed Frozen field to json:"-" to prevent default serialization; added FrozenFrontend *bool with json:"frozen,omitempty" for conditional exposure
• Serialization: Modified Preprocess() to set FrozenFrontend only for admin users
• Docs: Regenerated Swagger specs

Behavior

// Non-admin response
{"id": 1, "hidden": false, "locked": false, ...}

// Admin response  
{"id": 1, "hidden": false, "locked": false, "frozen": true, ...}

The implementation follows the fail-safe pattern: if user context is unavailable, the field is omitted.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG] 后端不应当向前端返回已冻结信息</issue_title>
<issue_description></issue_description>

<agent_instructions>Keep modifications minimal.</agent_instructions>

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

• Fixes [BUG] 后端不应当向前端返回已冻结信息 #198

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[Copilot]

Pull request overview

This PR implements access control for the Frozen field on holes, restricting visibility to administrators only. The implementation follows a fail-safe pattern where the field is omitted from API responses unless the user is confirmed to be an admin.

Key Changes:

• Modified the Frozen field serialization to use a dual-field pattern: database field excluded from JSON (json:"-") and a separate pointer field (FrozenFrontend) for conditional frontend exposure
• Updated Preprocess() to conditionally populate FrozenFrontend only for admin users
• Updated API documentation to reflect the admin-only nature of the frozen field

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
models/hole.go	Changed Frozen field to use json:"-", added FrozenFrontend *bool with json:"frozen,omitempty", and updated Preprocess() to set field only for admins
docs/swagger.yaml	Updated frozen field description from implementation detail to "admin-only visibility"
docs/swagger.json	Updated frozen field description to match swagger.yaml changes
docs/docs.go	Updated frozen field description in generated documentation
.gitignore	Added compiled binary outputs (treehole and treehole.exe) to gitignore

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[ppolariss]

直接改 frozen，要不前端还得改