fix(auth): align the social-login surfaces with the reference theme

The "other login methods" block drifted from zibll on three axes. Gitee was
mapped to fa-code-branch because FA5 Free ships no Gitee brand glyph, so the
button showed a generic branch icon; Google showed the monochrome FA glyph
instead of the reference's multi-colour mark. The modal also printed an
implicit agreement line under the social buttons, which the reference guest
card does not have. And the top-nav user popover built its own
.social-login-divider / .oauth-row / .oauth-btn markup and then wrapped that
in a second separator and .social_loginbar, so the block rendered nested and
unlike the reference.

aksrt_brand_icon() now routes zibsvg-/customsvg- values through the shared
icon renderer, and the brand map resolves gitee to zibsvg-gitee and google to
zibsvg-google-color. Both sprite keys already exist in the runtime symbol
sheet, which the loader pulls in on every frontend page. Because
get_auth_providers_data() and binding_row() both go through
aksrt_brand_icon(), one map change fixes the icon on the modal, the user card,
the top-nav popover, the user-center binding list and the profile social
links.

render_social_buttons() is rewritten to the reference shape: an optional
.social-separator, a .social_loginbar, and one .social-login-item <type>
toggle-radius anchor per enabled provider with rel="nofollow" and a
"<label>登录" title. oauth_button_lg switches to the button-lg variant with a
label, and the WeChat entry carries qrcode-signin so auth.js opens the QR
panel instead of navigating, matching the reference. The navbar and the link
apply modal now append the block verbatim instead of re-wrapping it, and the
user-card loop adopts the same item attributes. The retired
.social-login-divider / .oauth-row / .oauth-btn rules are dropped from
base-1.css, and the binding-list icon rule gains an svg selector so the
sprite icons keep the 22px the FA glyphs had.

Verification: node --test across widget-system, navigation, admin,
asset-ledger, dev, front-submit and visual (613 tests), plus php -l on every
changed PHP file. Extended the auth source contract with the agreement-line,
brand-icon and popover-structure cases, and pinned the user-card guest
markup.

tests/widget-system/auth-source-contract.test.cjs

@@ -239,3 +239,58 @@ test('OAuth frontend is accessible, redirect-aware, and removes retired provider
   assert.doesNotMatch(signCss + mainCss, /social-login-item[^\n{]*(?:baidu|alipay)|social-login-item\.(?:baidu|alipay)/i);
   assert.match(mainCss, /\.pay-box \.but\.baidu/);
 });
+
+test('the social-login area drops the implicit agreement line', () => {
+  const shared = read('templates/parts/auth-content.php');
+  const userRenderer = read('src/WidgetSystem/Renderers/UserRenderer.php');
+
+  // The reference shows no agreement copy under the social buttons; only the
+  // registration panel keeps its own, and it stays reachable.
+  assert.doesNotMatch(shared, /使用社交账号登录即表示/);
+  assert.match(shared, /注册即表示/);
+  assert.match(shared, /name="agree_terms"[\s\S]*?required/);
+  assert.doesNotMatch(userRenderer, /使用社交账号登录即表示|我已阅读并同意/);
+});
+
+test('brand icons resolve Gitee and Google to the reference SVG sprite', () => {
+  const icons = read('inc/helpers/aksrt-icons.php');
+  const sprites = read('assets/js/runtime/svg-icon.js');
+
+  // FA5 Free ships no Gitee brand glyph and no multi-colour Google mark, so both
+  // resolve to the theme's own symbol sheet exactly like the reference does.
+  assert.match(icons, /'gitee'\s*=>\s*'zibsvg-gitee'/);
+  assert.match(icons, /'google'\s*=>\s*'zibsvg-google-color'/);
+  assert.match(icons, /'github'\s*=>\s*'fa fab fa-github'/);
+  assert.match(icons, /'wechat'\s*=>\s*'fa fab fa-weixin'/);
+  assert.match(sprites, /aksrt_svgs\['gitee'\]/);
+  assert.match(sprites, /aksrt_svgs\['google-color'\]/);
+  // Sprite values must reach the shared icon renderer instead of being wrapped
+  // in a bogus <i class="zibsvg-…">.
+  assert.match(icons, /strpos\(\$class, 'zibsvg-'\) === 0[\s\S]*?aksrt_icon_markup\(\$class, \$extra_classes\)/);
+});
+
+test('the top-nav user popover reproduces the reference quick-login block', () => {
+  const oauth = read('src/Auth/OAuth.php');
+  const header = read('inc/helpers/header/aksrt-header-navbar.php');
+  const links = read('inc/helpers/aksrt-links.php');
+  const legacyCss = read('assets/css/frontend/pages/base-1.css');
+
+  assert.match(oauth, /social-separator separator muted-3-color em09 mt10/);
+  assert.match(oauth, /'<div class="social_loginbar">'/);
+  assert.match(oauth, /'social-login-item ' \. \$type/);
+  assert.match(oauth, /' button-lg' : ' toggle-radius'/);
+  assert.match(oauth, /rel="nofollow"/);
+  assert.match(oauth, /qrcode-signin/);
+  assert.match(oauth, /oauth_button_lg/);
+
+  // Callers append the block verbatim — no hand-rolled separator or wrapper.
+  assert.match(header, /render_social_buttons\(__\('快速登录', 'aksrt'\)\)/);
+  assert.doesNotMatch(header, /social-separator|social_loginbar/);
+  assert.match(links, /render_social_buttons\(__\('使用以下方式快速登录', 'aksrt'\)\)/);
+  assert.doesNotMatch(links, /social_loginbar/);
+
+  // The retired .social-login-divider / .oauth-row / .oauth-btn markup and its
+  // stylesheet are gone.
+  assert.doesNotMatch(oauth, /oauth-row|oauth-btn|social-login-divider/);
+  assert.doesNotMatch(legacyCss, /\.oauth-row|\.oauth-btn|\.social-login-divider/);
+});