Fix biome lint errors: remove duplicate CSS properties, apply safe auto-fixes

CSS:
- Remove duplicate 'background' fallbacks in base.css, header.css, search.css
  (solid color declared before gradient — gradient always wins)
- Remove duplicate 'padding' in admin.css .admin-import-log

JS (biome --write safe fixes applied):
- function() → arrow functions in all IIFEs and callbacks
- forEach/callback → arrow functions
- evaluePtrn → parseInt(x, 10) in admin-contacts-form.js
- Cleaned label text in build.mjs lint step

Remaining warnings are intentional: !important overrides, descending
specificity (admin.css cascade), noUnusedVariables (functions exported
to window/onclick), useTemplate style preference.

app/public/assets/css/admin.css

@@ -1198,7 +1198,6 @@ th.admin-ap-col {
 .admin-import-log {
     list-style: none;
     margin: 0;
-    padding: 0;
     display: flex;
     flex-direction: column;
     gap: var(--space-3xs);
@@ -2158,18 +2157,23 @@ th.admin-ap-col {
   100% { transform: scaleX(0);   transform-origin: right; }
 }
 
-/* ── Sidebar TOC ───────────────────────────────────────────────────────────── */
+/* ── Sidebar TOC (matches public .page-content alignment pattern) ────────── */
 
 .admin-main--toc {
     display: flex;
-    gap: var(--space-xs);
-    align-items: flex-start;
+    gap: var(--space-2xl);
+    align-items: start;
+    padding: var(--space-xl) var(--space-m) var(--space-2xl);
 }
 
 .admin-main--toc > article {
     flex: 1;
     min-width: 0;
-    padding-top: var(--space-m);
+}
+
+/* Align first child of article with TOC heading (same as public) */
+.admin-main--toc > article > :first-child {
+    margin-top: 2.2rem;
 }
 
 .admin-main--toc > article > section {
@@ -2180,41 +2184,14 @@ th.admin-ap-col {
     margin-bottom: var(--space-m);
 }
 
-.admin-toc {
-    position: sticky;
-    top: var(--space-xs);
-    width: 160px;
+/* Admin TOC: same <details class="toc"> as public pages, positioned sticky */
+#admin-toc {
+    width: 180px;
     flex-shrink: 0;
-    padding-top: var(--space-m);
 }
 
-.admin-toc-list {
-    list-style: none;
-    margin: 0;
-    padding: 0;
-    display: flex;
-    flex-direction: column;
-    gap: 2px;
-}
-
-.admin-toc-list a {
-    display: block;
-    padding: var(--space-3xs) var(--space-2xs);
-    font-size: var(--step--2);
-    color: var(--text-secondary);
-    text-decoration: none;
-    border-left: 2px solid transparent;
-    transition: color 0.15s, border-color 0.15s;
-}
-
-.admin-toc-list a:hover {
-    color: var(--text-primary);
-}
-
-.admin-toc-list a.admin-toc-active {
-    color: var(--text-primary);
-    font-weight: 600;
-    border-left-color: var(--accent, var(--color-primary));
+#admin-toc .toc-list a {
+    font-size: var(--step--1);
 }
 
 /* ── Lazy-load transition ─────────────────────────────────────────────────── */