fix: web/ quick wins — CSS cleanup, ARIA tabs, and file header comments

CSS:
- Remove duplicate li::before block in app-search.css
- Fix typo: search-reuslt → search-result in app-search.css
- Remove commented-out CSS rules in app-flash.css
- Add descriptive header comment to all 27 CSS component files

JS:
- Complete WAI-ARIA Tabs pattern: generate IDs, add aria-controls on
  tab buttons and aria-labelledby on tab panels (app-tabs.js)
- Add JSDoc header comments to ~33 JS files (core + components)
- Add explanatory block comment to app-boot.js (why classic IIFE)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/js/components/app-tabs.js

@@ -90,13 +90,18 @@ export function initTabs(root = document) {
     };
 
     // ----------------------------------------------------------------
-    //  ARIA: role="tablist" on the nav, not the outer container
+    //  ARIA: role, aria-controls, aria-labelledby (WAI-ARIA Tabs pattern)
     // ----------------------------------------------------------------
     const nav = container.querySelector('.app-tabs-nav');
+    const tabIdPrefix = container.id || `tabs-${Math.random().toString(36).slice(2, 8)}`;
 
-    // Initialize tabs
     tabs.forEach(tab => {
+      const tabName = tab.dataset.tab;
+      const tabId = `${tabIdPrefix}-tab-${tabName}`;
+      const panelId = `${tabIdPrefix}-panel-${tabName}`;
       tab.setAttribute('role', 'tab');
+      tab.id = tabId;
+      tab.setAttribute('aria-controls', panelId);
       tab.addEventListener('click', (e) => {
         e.preventDefault();
         activateTab(tab.dataset.tab);
@@ -106,7 +111,12 @@ export function initTabs(root = document) {
     });
 
     panels.forEach(panel => {
+      const panelName = panel.dataset.tabPanel;
+      const panelId = `${tabIdPrefix}-panel-${panelName}`;
+      const tabId = `${tabIdPrefix}-tab-${panelName}`;
       panel.setAttribute('role', 'tabpanel');
+      panel.id = panelId;
+      panel.setAttribute('aria-labelledby', tabId);
     });
 
     if (nav) {