feat: 足迹 Footprints 个人留痕系统

桌面应用(Tauri+React+SQLite)：时间线/记录/学年学科成绩梯度/统计/类型与字段模板/附件内容寻址/详情视图/PWA

同步服务端(sync-server)：多用户+邀请码/LWW推拉/seq游标/附件去重/Docker部署

多端同步地基：uuid v7/HLC混合逻辑时钟/软删除墓碑/sync_oplog，Node与Rust双端一致并通过自动化测试

app/public/manifest.webmanifest

@@ -0,0 +1,30 @@
+{
+  "name": "足迹 Footprints",
+  "short_name": "足迹",
+  "description": "个人成长足迹档案：记录、检索、量化、导出",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "portrait-primary",
+  "background_color": "#101216",
+  "theme_color": "#3056d3",
+  "lang": "zh-CN",
+  "icons": [
+    {
+      "src": "/icons/pwa-192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/icons/pwa-512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    },
+    {
+      "src": "/icons/maskable-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ]
+}

app/public/sw.js

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+// PWA Service Worker v2
+// - 页面导航：网络优先（构建更新后强制拿到新 index.html），离线才回落缓存
+// - 静态资源：缓存优先
+// - /api：直连不缓存
+const CACHE = 'fp-static-v2';
+const CORE = ['/', '/manifest.webmanifest', '/icons/pwa-192.png', '/icons/pwa-512.png'];
+
+self.addEventListener('install', (e) => {
+  self.skipWaiting();
+  e.waitUntil(caches.open(CACHE).then((c) => c.addAll(CORE)));
+});
+
+self.addEventListener('activate', (e) => {
+  e.waitUntil(
+    caches.keys()
+      .then((ks) => Promise.all(ks.filter((k) => k !== CACHE).map((k) => caches.delete(k))))
+      .then(() => self.clients.claim())
+  );
+});
+
+self.addEventListener('fetch', (e) => {
+  const url = new URL(e.request.url);
+  if (e.request.method !== 'GET' || url.pathname.startsWith('/api')) return;
+
+  if (e.request.mode === 'navigate') {
+    e.respondWith(
+      fetch(e.request).then((res) => {
+        const copy = res.clone();
+        caches.open(CACHE).then((c) => c.put('/index.html', copy));
+        return res;
+      }).catch(() => caches.match('/index.html').then((h) => h || caches.match('/')))
+    );
+    return;
+  }
+
+  e.respondWith(
+    caches.match(e.request).then((hit) => hit || fetch(e.request).then((res) => {
+      if (res.ok && url.origin === location.origin) {
+        const copy = res.clone();
+        caches.open(CACHE).then((c) => c.put(e.request, copy));
+      }
+      return res;
+    }))
+  );
+});