fix(api): 修復 10 個 Lint 錯誤 (imports 排序 + unused imports + set comprehension)

- F401: 移除未使用的 imports (TerminalSessionStatus, AutoApproveDecision, TerminalSession)
- I001: 修正 import blocks 排序
- C401: set(generator) → {set comprehension}

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/models/terminal.py

@@ -17,7 +17,6 @@ from typing import Any
 
 from pydantic import BaseModel, Field
 
-
 # =============================================================================
 # Enums
 # =============================================================================