feat(ui): brand atmosphere — login grid + floating glow, logo gradient edge, inline SVG favicon (v1.20 G)

[argszero]

Summary

Item G (final) of rant 2026-08-17T20:46:57 (UI/UE 第五轮多角度深化, v1.20): 品牌与登录页氛围 — brand atmosphere for the login page + favicon.

• Login page 渐变网格 background: .login-view::before — 44px faint grid (two 1px linear-gradient layers) with a radial mask fading the edges, pointer-events:none
• 微光浮动: .login-view::after — accent glow orb (rgba(78,205,196,.16) radial gradient) with login-float keyframes (10s translate + scale alternate); frozen under prefers-reduced-motion via the existing global rule
• Card above atmosphere: .login-card { position: relative; z-index: 1 }
• Logo 渐变描边/发光 (login + sidebar shared): .logo gains an accent edge ring (0 0 0 1.5px) + outer glow (0 0 14px), .logo::after inner top highlight (inset 0 1px 0 rgba(255,255,255,.30)) + bottom shadow (inset 0 -1px 0 rgba(0,0,0,.14))
• favicon inline SVG data URI: <link rel="icon" type="image/svg+xml" href="data:image/svg+xml,…"> — gradient rounded square + AT text, zero external files

Rant reference (verbatim)

G. 品牌与登录页氛围 — CSS 渐变网格 + 微光浮动；logo 渐变描边/发光；favicon inline SVG data URI

Verification

• DOM-stub smoke test: 26/26 assertions (favicon data URI gradient/AT/type; ::before grid + mask; ::after float animation; card z-index; logo ring/glow/inset; reduced-motion coverage; existing login structure intact)
• node --check ui/js/app.js ✓ (no JS change), CSS braces balanced ✓
• cargo test ✓ (1 passed), cargo fmt --check ✓
• Docs: docs/user-stories.md v1.20 entry (G added, wave closed), ui/README.md「品牌与登录页氛围约定」section

Progress on rant 20:46:57: A–G all seven items merged (#63/#65/#66/#67/#68/#69/#70) — wave complete.