refactor: 重组项目文件结构

- 将项目概述文件移至根目录
- 将算法学习指南移至 questions 目录
- 将面试准备进度移至根目录
- 删除空的 questions 文件
- 更新 Obsidian 主题配置

.obsidian/themes/Minimal/manifest.json

@@ -0,0 +1,8 @@
+{
+	"name": "Minimal",
+	"version": "8.1.6",
+	"minAppVersion": "1.9.0",
+	"author": "@kepano",
+	"authorUrl": "https://twitter.com/kepano",
+	"fundingUrl": "https://www.buymeacoffee.com/kepano"
+}