fix(frontend): keep the widget link color off the check-in badge

sidebar.css paints .widget a with --color-ink-2 (specificity 0,1,1), which
out-specifies the .jb-* color group (0,1,0) the badge relies on for its white
ink. The user-card widget carries the .widget class, so the check-in bookmark
rendered dark-gray text on the orange gradient on widget pages. zibll sets no
link color on zib-widget anchors at all.

sidebar.css already restores .but colors for exactly this reason; extend that
restoration to .img-badge so the badge keeps its own --this-color. Rebuild the
homepage bundle and extend the badge contract test.

tests/widget-system/user-card-checkin-badge-contract.test.cjs

@@ -64,6 +64,22 @@ test('the badge typography is pinned to the reference bootstrap body values', ()
   )
 })
 
+test('the sidebar widget link color does not recolor the check-in badge', () => {
+  // .widget a (sidebar.css, shipped in the homepage bundle) out-specifies the
+  // .jb-* color group, so the badge would paint --color-ink-2 instead of the
+  // white --this-color; the established .but restoration must cover img-badge.
+  const sidebar = read('assets/css/frontend/sidebar.css')
+  const start = sidebar.indexOf('.widget a.but')
+  assert.notEqual(start, -1, 'missing the .widget a color restoration')
+  const block = sidebar.slice(start, sidebar.indexOf('}', start))
+  assert.match(block, /\.widget a\.but,/)
+  assert.match(block, /\.widget a\.img-badge/)
+  assert.match(block, /color:\s*var\(--this-color/)
+
+  const bundle = read('assets/css/build/homepage.min.css')
+  assert.match(bundle, /\.widget a\.but,\.widget a\.img-badge\{color:var\(--this-color, #fff\)\}/)
+})
+
 test('the user-card check-in badge renders without the dead is-done class and bare span', () => {
   const userbox = read('inc/helpers/aksrt-header-userbox.php')
   const fnStart = userbox.indexOf('function aksrt_header_user_checkin_btn')