feat(header): icon nav redesign + migrate icons mdi→lucide

- Header desktop nav: social icons grouped in a wald-tinted pill with
  labels, active-state (aria-current + bold), opacity hover (no per-item bg)
- Mobile overlay: social links as icon+label rows with active-state
- Search button: lucide:search, icon-only
- Migrate all icons mdi→lucide app-wide (234 refs); brand/language logos
  (google, whatsapp, mastodon, telegram, language-*) stay on mdi
- generate-icons: emit mdi + lucide subsets; add @iconify-json/lucide
- iconify-offline: register lucide collection
- scripts/icon-map|validate|apply: reusable migration tooling

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/icon-map.mjs

@@ -0,0 +1,104 @@
+// mdi -> lucide migration map. Names without a sensible lucide pendant
+// (brand/language logos) intentionally stay on mdi — listed in KEEP_MDI.
+export const KEEP_MDI = new Set([
+  'google', 'whatsapp', 'mastodon', // brands missing in lucide
+  'language-javascript', 'language-python', 'language-rust', // language logos
+]);
+
+export const MAP = {
+  'account-group-outline': 'users',
+  'alert-circle': 'circle-alert',
+  'alert-circle-outline': 'circle-alert',
+  'arrow-right': 'arrow-right',
+  'arrow-top-right': 'arrow-up-right',
+  'calendar': 'calendar',
+  'calendar-blank': 'calendar',
+  'calendar-clock': 'calendar-clock',
+  'calendar-export': 'calendar-arrow-up',
+  'calendar-month-outline': 'calendar',
+  'calendar-plus': 'calendar-plus',
+  'calendar-search': 'calendar-search',
+  'card-account-details-outline': 'id-card',
+  'check': 'check',
+  'check-circle': 'circle-check',
+  'check-decagram': 'badge-check',
+  'chevron-down': 'chevron-down',
+  'chevron-left': 'chevron-left',
+  'chevron-right': 'chevron-right',
+  'chevron-up': 'chevron-up',
+  'clock-alert-outline': 'alarm-clock',
+  'clock-outline': 'clock',
+  'clock-remove-outline': 'clock-fading',
+  'close': 'x',
+  'cloud': 'cloud',
+  'cloud-off-outline': 'cloud-off',
+  'code-json': 'braces',
+  'comment-outline': 'message-circle',
+  'comment-text-outline': 'message-square-text',
+  'console': 'terminal',
+  'content-copy': 'copy',
+  'content-save-outline': 'save',
+  'cursor-default-click': 'mouse-pointer-click',
+  'cursor-default-click-outline': 'mouse-pointer-click',
+  'database-outline': 'database',
+  'domain': 'building-2',
+  'download': 'download',
+  'download-outline': 'download',
+  'drag-vertical': 'grip-vertical',
+  'email': 'mail',
+  'email-outline': 'mail',
+  'facebook': 'facebook',
+  'file-document-edit-outline': 'file-pen',
+  'file-document-outline': 'file-text',
+  'file-download': 'file-down',
+  'file-excel-box': 'file-spreadsheet',
+  'file-image': 'file-image',
+  'file-outline': 'file',
+  'file-pdf-box': 'file-text',
+  'file-powerpoint-box': 'presentation',
+  'file-word-box': 'file-text',
+  'flag-outline': 'flag',
+  'folder-zip': 'folder-archive',
+  'format-text-variant-outline': 'type',
+  'home': 'house',
+  'home-group': 'house',
+  'home-outline': 'house',
+  'image-outline': 'image',
+  'information-outline': 'info',
+  'link': 'link',
+  'link-variant': 'link',
+  'loading': 'loader-circle',
+  'magnify': 'search',
+  'magnify-plus': 'zoom-in',
+  'map': 'map',
+  'map-marker': 'map-pin',
+  'map-marker-outline': 'map-pin',
+  'map-outline': 'map',
+  'menu': 'menu',
+  'open-in-new': 'external-link',
+  'pencil-outline': 'pencil',
+  'phone': 'phone',
+  'phone-outline': 'phone',
+  'play': 'play',
+  'printer': 'printer',
+  'printer-outline': 'printer',
+  'qrcode': 'qr-code',
+  'refresh': 'refresh-cw',
+  'reply': 'reply',
+  'robot-outline': 'bot',
+  'rss': 'rss',
+  'ruler-square': 'ruler',
+  'share-variant': 'share-2',
+  'share-variant-outline': 'share-2',
+  'shield-check-outline': 'shield-check',
+  'sort-alphabetical-ascending': 'arrow-down-a-z',
+  'transmission-tower': 'radio-tower',
+  'trash-can-outline': 'trash-2',
+  'tune': 'sliders-horizontal',
+  'tune-variant': 'sliders-horizontal',
+  'vector-square': 'square-dashed',
+  'video': 'video',
+  'wind-turbine': 'fan',
+  'xml': 'code',
+  'youtube': 'youtube',
+};