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/models.py

@@ -406,9 +406,9 @@ class ZhihuContent(Base):
     last_modify_ts = Column(BigInteger)
 
     # persist-1<persist1@126.com>
-    # 原因：修复 ORM 模型定义错误，确保与数据库表结构一致。
-    # 副作用：无
-    # 回滚策略：还原此行
+    # Reason: Fixed ORM model definition error, ensuring consistency with database table structure.
+    # Side effects: None
+    # Rollback strategy: Restore this line
 
 class ZhihuComment(Base):
     __tablename__ = 'zhihu_comment'