搜索历史持久化

[robinv8]

SearchViewModel 有 searchHistory 属性，但不确定是否持久化（可能只在内存中）。需要使用 UserDefaults 持久化搜索历史。

Status

• Task Key: search-history-persist
• Spec Revision: aaa5e6d9
• Approved Revision: aaa5e6d9
• Approval State: approved
• Current Stage: definition
• Next Stage: run
• Workflow Entry State: ready_to_start
• Attempt Count: 0
• Max Retry Count: 3
• Code Publication State: not_applicable
• Close On Done: auto
• Depends On: none

Dependencies

(no dependencies)

Acceptance Criteria

• App 重启后搜索历史保留
• 历史记录上限 20 条，超出时淘汰最旧的
• 搜索后自动添加到历史（去重，移到最前）
• 支持单条删除和全部清除

Verification

• 重启 App 验证历史保留
• 添加超过 20 条验证淘汰最旧的
• 测试重复搜索的去重和排序
• 测试单条删除和全部清除

Source

• Spec: docs/prd/ios-improvement.md
• Parent Issue: (no parent)

[robinv8]

Task published from spec docs/prd/ios-improvement.md at revision aaa5e6d9.

iron_tree:
  version: 1
  task_key: search-history-persist
  issue_number: 25
  spec_revision: aaa5e6d9
  approved_revision: aaa5e6d9
  sequence: 1
  event: task_published
  current_stage: definition
  next_stage: run
  workflow_entry_state: ready_to_start
  approval_state: approved
  attempt_count: 0
  max_retry_count: 3
  code_publication_state: not_applicable
  pass_fail_outcome: null
  completion_basis: null
  code_ref: null