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/src/styles/theme.css

@@ -0,0 +1,135 @@
+@import 'tailwindcss';
+
+/* ============================================
+   Footprints 设计系统 v2 —— 企业级视觉规范
+   栅格 4px · 控件高 28px · 正文 14px · 圆角 6/8
+   ============================================ */
+
+@theme inline {
+  --color-bg: var(--bg);
+  --color-surface: var(--surface);
+  --color-surface-2: var(--surface-2);
+  --color-surface-3: var(--surface-3);
+  --color-line: var(--border);
+  --color-line-strong: var(--border-strong);
+  --color-ink-1: var(--text-1);
+  --color-ink-2: var(--text-2);
+  --color-ink-3: var(--text-3);
+  --color-brand: var(--brand);
+  --color-brand-hover: var(--brand-hover);
+  --color-brand-subtle: var(--brand-subtle);
+  --color-brand-text: var(--brand-text);
+  --color-success: var(--success);
+  --color-success-subtle: var(--success-subtle);
+  --color-warning: var(--warning);
+  --color-warning-subtle: var(--warning-subtle);
+  --color-danger: var(--danger);
+  --color-danger-subtle: var(--danger-subtle);
+
+  --radius-sm: 4px;
+  --radius-md: 6px;
+  --radius-lg: 8px;
+
+  --shadow-card: 0 1px 2px rgba(16, 24, 40, 0.04), 0 1px 3px rgba(16, 24, 40, 0.05);
+  --shadow-pop: 0 12px 32px rgba(16, 24, 40, 0.16), 0 2px 8px rgba(16, 24, 40, 0.08);
+}
+
+/* ---------- 亮色 ---------- */
+:root {
+  --bg: #f4f5f7;
+  --surface: #ffffff;
+  --surface-2: #f9fafb;
+  --surface-3: #eff1f4;
+  --border: #e5e8ec;
+  --border-strong: #ccd3dc;
+  --text-1: #15181d;
+  --text-2: #454e5c;
+  --text-3: #7e8798;
+  --brand: #3056d3;
+  --brand-hover: #2748b8;
+  --brand-subtle: #eef2ff;
+  --brand-text: #2748b8;
+  --success: #15803d;
+  --success-subtle: #ecfdf3;
+  --warning: #b45309;
+  --warning-subtle: #fffaeb;
+  --danger: #dc2626;
+  --danger-subtle: #fef3f2;
+}
+
+/* ---------- 暗色 ---------- */
+.dark {
+  --bg: #0e1013;
+  --surface: #15181e;
+  --surface-2: #1a1e25;
+  --surface-3: #22272f;
+  --border: #262c35;
+  --border-strong: #3a424f;
+  --text-1: #e8ebf1;
+  --text-2: #a2abb9;
+  --text-3: #6d7684;
+  --brand: #7c93f5;
+  --brand-hover: #94a8f8;
+  --brand-subtle: #1c2340;
+  --brand-text: #a3b4f8;
+  --success: #4ade80;
+  --success-subtle: #12251a;
+  --warning: #fbbf24;
+  --warning-subtle: #2a2213;
+  --danger: #f87171;
+  --danger-subtle: #2c1618;
+}
+
+html, body, #root { height: 100%; }
+
+body {
+  background: var(--bg);
+  color: var(--text-1);
+  font-family: system-ui, 'Segoe UI Variable Text', 'Segoe UI', 'Microsoft YaHei UI', 'Microsoft YaHei', 'PingFang SC', sans-serif;
+  font-size: 14px;
+  line-height: 1.55;
+  letter-spacing: 0.005em;
+  -webkit-font-smoothing: antialiased;
+  text-rendering: optimizeLegibility;
+}
+
+/* 标题排版：紧凑字距 */
+h1, h2, h3 {
+  letter-spacing: -0.01em;
+  text-wrap: balance;
+}
+
+/* 数字统一等宽，对齐敏感场景（表格/指标卡） */
+.num {
+  font-variant-numeric: tabular-nums;
+  font-feature-settings: 'tnum' 1;
+}
+
+::selection { background: color-mix(in srgb, var(--brand) 22%, transparent); }
+
+/* 滚动条：更纤细，悬停加深 */
+* { scrollbar-width: thin; scrollbar-color: var(--border-strong) transparent; }
+*::-webkit-scrollbar { width: 6px; height: 6px; }
+*::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 3px; }
+*::-webkit-scrollbar-thumb:hover { background: var(--text-3); }
+*::-webkit-scrollbar-track { background: transparent; }
+
+:focus-visible {
+  outline: 2px solid color-mix(in srgb, var(--brand) 55%, transparent);
+  outline-offset: 1px;
+}
+
+.animate-in { animation: fp-fade-slide-in 0.18s ease-out; }
+
+@keyframes fp-fade-slide-in {
+  from { opacity: 0; transform: translateY(4px); }
+  to { opacity: 1; transform: none; }
+}
+
+/* 数字输入框去掉浏览器步进按钮的视觉噪音 */
+input[type='number']::-webkit-outer-spin-button,
+input[type='number']::-webkit-inner-spin-button {
+  -webkit-appearance: none;
+  margin: 0;
+}
+input[type='number'] { -moz-appearance: textfield; appearance: textfield; }