i18n: translate all Chinese comments, docstrings, and logger messages to English

Comprehensive translation of Chinese text to English across the entire codebase:

- api/: FastAPI server documentation and logger messages
- cache/: Cache abstraction layer comments and docstrings
- database/: Database models and MongoDB store documentation
- media_platform/: All platform crawlers (Bilibili, Douyin, Kuaishou, Tieba, Weibo, Xiaohongshu, Zhihu)
- model/: Data model documentation
- proxy/: Proxy pool and provider documentation
- store/: Data storage layer comments
- tools/: Utility functions and browser automation
- test/: Test file documentation

Preserved: Chinese disclaimer header (lines 10-18) for legal compliance

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

database/db.py

@@ -17,9 +17,9 @@
 # 使用本代码即表示您同意遵守上述原则和LICENSE中的所有条款。
 
 # persist-1<persist1@126.com>
-# 原因：将 db.py 改造为模块，移除直接执行入口，修复相对导入问题。
-# 副作用：无
-# 回滚策略：还原此文件。
+# Reason: Refactored db.py into a module, removed direct execution entry point, fixed relative import issues.
+# Side effects: None
+# Rollback strategy: Restore this file.
 import asyncio
 import sys
 from pathlib import Path