feat: add auto-update system with release checking, notification UI, and install-type-aware apply

- Abstract ReleaseProvider interface (Gitea impl, swappable for GitHub/GitLab)
- Background UpdateService with periodic checks, debounce, dismissed version persistence
- Install type detection (installer/portable/docker/dev) with platform-aware asset matching
- Download with progress events, silent NSIS reinstall, portable ZIP/tarball swap scripts
- Version badge pulse animation, dismissible banner with icon buttons, Settings > Updates tab
- Single source of truth: pyproject.toml version via importlib.metadata, CI stamps tag with sed
- API: GET/POST status, check, dismiss, apply, GET/PUT settings
- i18n: en, ru, zh (27+ keys each)

server/src/wled_controller/static/locales/zh.json

@@ -1844,6 +1844,43 @@
     "appearance.bg.scanlines": "扫描线",
     "appearance.bg.applied": "背景效果已应用",
 
+    "settings.tab.updates": "更新",
+    "update.status_label": "更新状态",
+    "update.current_version": "当前版本：",
+    "update.badge_tooltip": "有新版本可用 — 点击查看详情",
+    "update.available": "版本 {version} 可用",
+    "update.up_to_date": "已是最新版本",
+    "update.prerelease": "预发布",
+    "update.view_release": "查看发布",
+    "update.dismiss": "忽略",
+    "update.check_now": "检查更新",
+    "update.check_error": "检查更新失败",
+    "update.last_check": "上次检查",
+    "update.never": "从未",
+    "update.release_notes": "发布说明",
+    "update.auto_check_label": "自动检查设置",
+    "update.auto_check_hint": "在后台定期检查新版本。",
+    "update.enable": "启用自动检查",
+    "update.interval_label": "检查间隔",
+    "update.channel_label": "频道",
+    "update.channel.stable": "稳定版",
+    "update.channel.stable_desc": "仅稳定版本",
+    "update.channel.prerelease": "预发布",
+    "update.channel.prerelease_desc": "包括 alpha、beta 和 RC 版本",
+    "update.save_settings": "保存设置",
+    "update.settings_saved": "更新设置已保存",
+    "update.settings_save_error": "保存更新设置失败",
+    "update.apply_now": "立即更新",
+    "update.apply_confirm": "下载并安装版本 {version}？服务器将自动重启。",
+    "update.apply_error": "更新失败",
+    "update.applying": "正在应用更新…",
+    "update.downloading": "正在下载…",
+    "update.install_type_label": "安装类型：",
+    "update.install_type.installer": "Windows 安装程序",
+    "update.install_type.portable": "便携版",
+    "update.install_type.docker": "Docker",
+    "update.install_type.dev": "开发环境",
+
     "color_strip": {
         "notification": {
             "search_apps": "搜索通知应用…"