📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/svgo/plugins/removeAttributesBySelector.js

@@ -0,0 +1,70 @@
+'use strict';
+
+exports.type = 'perItem';
+
+exports.active = false;
+
+exports.description = 'removes attributes of elements that match a css selector';
+
+
+/**
+ * Removes attributes of elements that match a css selector.
+ *
+ * @param {Object} item current iteration item
+ * @param {Object} params plugin params
+ * @return {Boolean} if false, item will be filtered out
+ *
+ * @example
+ * <caption>A selector removing a single attribute</caption>
+ * plugins:
+ *   - removeAttributesBySelector:
+ *       selector: "[fill='#00ff00']"
+ *       attributes: "fill"
+ *
+ * <rect x="0" y="0" width="100" height="100" fill="#00ff00" stroke="#00ff00"/>
+ *   ↓
+ * <rect x="0" y="0" width="100" height="100" stroke="#00ff00"/>     
+ *
+ * <caption>A selector removing multiple attributes</caption>
+ * plugins:
+ *   - removeAttributesBySelector:
+ *       selector: "[fill='#00ff00']"
+ *       attributes:
+ *         - fill
+ *         - stroke
+ *
+ * <rect x="0" y="0" width="100" height="100" fill="#00ff00" stroke="#00ff00"/>
+ *   ↓
+ * <rect x="0" y="0" width="100" height="100"/>     
+ *
+ * <caption>Multiple selectors removing attributes</caption>
+ * plugins:
+ *   - removeAttributesBySelector:
+ *       selectors:
+ *         - selector: "[fill='#00ff00']"
+ *           attributes: "fill"
+ *
+ *         - selector: "#remove"
+ *           attributes:
+ *             - stroke
+ *             - id
+ *
+ * <rect x="0" y="0" width="100" height="100" fill="#00ff00" stroke="#00ff00"/>
+ *   ↓
+ * <rect x="0" y="0" width="100" height="100"/>
+ *
+ * @see {@link https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors|MDN CSS Selectors}
+ *
+ * @author Bradley Mease
+ */
+exports.fn = function(item, params) {
+
+    var selectors = Array.isArray(params.selectors) ? params.selectors : [params];
+
+    selectors.map(function(i) {
+        if (item.matches(i.selector)) {
+            item.removeAttr(i.attributes);
+        }
+    });
+
+};