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>

main.py

@@ -114,7 +114,7 @@ async def async_cleanup() -> None:
             except Exception as e:
                 error_msg = str(e).lower()
                 if "closed" not in error_msg and "disconnected" not in error_msg:
-                    print(f"[Main] 清理CDP浏览器时出错: {e}")
+                    print(f"[Main] Error cleaning up CDP browser: {e}")
 
         elif getattr(crawler, "browser_context", None):
             try:
@@ -122,7 +122,7 @@ async def async_cleanup() -> None:
             except Exception as e:
                 error_msg = str(e).lower()
                 if "closed" not in error_msg and "disconnected" not in error_msg:
-                    print(f"[Main] 关闭浏览器上下文时出错: {e}")
+                    print(f"[Main] Error closing browser context: {e}")
 
     if config.SAVE_DATA_OPTION in ("db", "sqlite"):
         await db.close()