feat: v0.2.3 — 浮动格式工具栏 + 10个新API + 德语翻译 + 类型修复

### Added
- 浮动格式工具栏：选中文本自动弹出 bold/italic/code/link/strikethrough
- 10 个新 API: getSelectedText/getCursorPosition/setCursorPosition/scrollToLine/selectLine/selectAll/replaceAll/replaceAllRegex/lineCount/getLine
- 2 个新事件: selectionChange / cursorMove
- 德语 (de) locale 完整翻译
- floatingToolbar 配置项（默认 true）

### Fixed
- onLinkClick 移除 as any，正式加入 EditorOptions/DEFAULTS
- 所有版本号统一为 0.2.3

### Tests
- core.test.ts: 183 → 214 (+31 tests)
- 总计 ~725 tests

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@metona-team/metona-editor",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "description": "Type-safe, lightweight, zero-dependency Markdown Editor. Desktop-first. React-free. Single-file bundle.",
   "type": "module",
   "main": "dist/metona-editor.js",