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>

media_platform/tieba/field.py

@@ -23,16 +23,16 @@ from enum import Enum
 
 class SearchSortType(Enum):
     """search sort type"""
-    # 按时间倒序
+    # Sort by time in descending order
     TIME_DESC = "1"
-    # 按时间顺序
+    # Sort by time in ascending order
     TIME_ASC = "0"
-    # 按相关性顺序
+    # Sort by relevance
     RELEVANCE_ORDER = "2"
 
 
 class SearchNoteType(Enum):
-    # 只看主题贴
+    # Only view main posts
     MAIN_THREAD = "1"
-    # 混合模式（帖子+回复）
+    # Mixed mode (posts + replies)
     FIXED_THREAD = "0"