feat(ui): visual polish — SVG nav icons, empty states, badges, cards (v1.15)

[argszero]

Summary

Visual polish (rant 2026-08-17T15:50:05, section A) — systematic visual improvement of the UI prototype:

1. Design system: consistent CSS variables (colors/radius/shadow/spacing) kept; deep-theme hierarchy verified (bg → card → border → accent).
2. Sidebar nav: emoji icons → uniform inline SVG icons (linear style, same 18px size, currentColor, hover/active states preserved; collapsed 64px sidebar is now properly icon-only).
3. Cards & tables: card hover micro-interaction (subtle shadow + border lift); table zebra striping + row hover highlight (hover wins over zebra).
4. Empty states: new empty-state component (icon + text + action button) applied to marketplace / sharing list / raise requests / transactions / API keys / departments / operator users — with wired actions: 清除筛选 (clear marketplace filters), 上架新 key (open share form), 生成新 Key (generate API key), 清除搜索 (clear dept search). Dashboard sharing empty also upgraded.
5. Badges: semantic color dot (ok/warn/danger/dim) for one-glance status reading.
6. Responsive: collapsed sidebar + horizontal table scroll kept; spacing adapts on narrow screens.

Self-verified: node --check passes, DOM smoke test (init path) runs without throwing, all $("#id") refs ↔ HTML ids cross-checked, no residual emoji nav icons, cargo test passes.

Related Issue

(no issue — host rant driven: 2026-08-17T15:50:05)

Changes

• SVG 图标统一（无 emoji 散落）；卡片/表格/徽章/空状态视觉提升
• docs/user-stories.md v1.15、ui/README 视觉约定同步

Tests

• cargo test 全部通过（1 passed）
• cargo fmt --check 通过（无 Rust 改动）
• UI 自测：node --check + DOM 冒烟 + id 交叉校验无缺失

Checklist

• 分支命名符合约定（feat/ui-polish-visual）
• Commit message 使用 Conventional Commits 格式
• 单一职责，改动最小化