feat(assets): 添加 SVG 图标和环境配置文件

- 新增 icons.svg 文件用于定义应用图标
- 添加 .env 配置文件设置 API 基础地址
- 配置图标视图框和路径数据
- 设置图标宽度为 100%，高度为 6

frontend/src/assets/icons/sunny.svg

@@ -0,0 +1 @@
+<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg t="1764820260653" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="13095" xmlns:xlink="http://www.w3.org/1999/xlink" width="16" height="16"><path d="M152.00256 792.00256l76.00128-77.99808 60.00128 60.00128-76.00128 77.99808z m317.99808 165.99552V832h83.99872v125.99808H470.00064zM512 233.99936c141.99808 0 256 114.00192 256 256s-114.00192 256-256 256-256-114.00192-256-256 114.00192-256 256-256zM854.00064 448h128v86.00064h-128V448z m-118.00064 326.00064l60.00128-57.99936 76.00128 76.00128-60.00128 60.00128z m136.00256-584.00256l-76.00128 76.00128-60.00128-60.00128 76.00128-76.00128z m-318.0032-165.99552v125.99808H470.00064V24.00256h83.99872z m-384 423.99744v86.00064h-128V448h128zM288 205.99808L227.99872 265.99936 151.99744 189.99808 211.99872 129.9968z" p-id="13096" fill="#ffa300"></path></svg>