feat: multi-OpenClaw CLI detection/binding + i18n infrastructure

Multi-OpenClaw Detection & Binding:
- Add resolve_openclaw_cli_path() and classify_cli_source() in utils.rs
- Support openclawCliPath binding in clawpanel.json (user selects CLI)
- VersionInfo now includes cli_path, cli_source, all_installations
- scan_all_installations() detects all OpenClaw installs on system
- Dashboard shows CLI source label + multi-install warning
- Settings page: CLI binding UI with auto-detect and manual selection
- dev-api.js synced with cli_path/cli_source fields for Web mode

i18n Infrastructure:
- Create src/lib/i18n.js core module (t(), setLang(), initI18n())
- Create src/locales/zh-CN.json and src/locales/en.json
- Sidebar fully i18n-ized (nav labels, sections, instance switcher)
- Dashboard stat cards fully i18n-ized
- Settings page: language switcher UI (live reload)
- initI18n() called in main.js on startup

src/main.js

@@ -14,6 +14,7 @@ import { api, checkBackendHealth, isBackendOnline, onBackendStatusChange } from
 import { version as APP_VERSION } from '../package.json'
 import { statusIcon } from './lib/icons.js'
 import { tryShowEngagement } from './components/engagement.js'
+import { initI18n } from './lib/i18n.js'
 
 // 样式
 import './style/variables.css'
@@ -27,8 +28,9 @@ import './style/debug.css'
 import './style/assistant.css'
 import './style/ai-drawer.css'
 
-// 初始化主题
+// 初始化主题 + 国际化
 initTheme()
+initI18n()
 
 /** HTML 转义，防止 XSS 注入 */
 function escapeHtml(str) {