feat: add event log panel, Chinese font support, and documentation

- Add EventLog.cs: scrollable event log panel showing game events
  - Color-coded entries for different event types
  - Toggle visibility, clear button, timestamps
  - Auto-scroll to newest entries

- Add Chinese font support (Source Han Sans SC)
  - SourceHanSansSC-Regular.otf font file
  - ChineseFontSetup.cs editor tool for TMP font asset generation
  - Configure as fallback font for TextMeshPro

- Fix particle system velocity curve warnings in WeatherEffects.cs
  - Ensure all velocity axes use consistent curve mode

- Add comprehensive README.md with project documentation
  - Architecture overview, features, tech stack
  - Quick start guide, Unity client structure
  - Communication protocol, development notes

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

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

unity-client/Assets/Scripts/UIManager.cs

@@ -28,6 +28,7 @@ namespace TheIsland.UI
         private Button _resetButton;
         private GameObject _notificationPanel;
         private TextMeshProUGUI _notificationText;
+        // EventLog 现在自己管理初始化
         #endregion
 
         #region State
@@ -149,6 +150,7 @@ namespace TheIsland.UI
             CreateTopBar();
             CreateBottomBar();
             CreateNotificationPanel();
+            // EventLog 自己管理初始化，不在这里创建
         }
 
         private void CreateTopBar()