Add JS tests, refactor SitemapController, extract JS modules

- Extract mobile-menu.js and tabs.js from app.js
- Add Vitest tests with happy-dom and v8 coverage (100% on modules)
- Add JS test step to CI frontend and SonarQube workflows
- SonarQube: add JS lcov coverage report path
- SitemapController: extract URLSET_TEMPLATE constant, deduplicate methods

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

assets/modules/mobile-menu.js

@@ -0,0 +1,16 @@
+export function initMobileMenu() {
+    const btn = document.getElementById('mobile-menu-btn')
+    const menu = document.getElementById('mobile-menu')
+    const iconOpen = document.getElementById('menu-icon-open')
+    const iconClose = document.getElementById('menu-icon-close')
+
+    if (btn && menu) {
+        btn.addEventListener('click', () => {
+            const isOpen = !menu.classList.contains('hidden')
+            menu.classList.toggle('hidden')
+            iconOpen.classList.toggle('hidden')
+            iconClose.classList.toggle('hidden')
+            btn.setAttribute('aria-expanded', String(!isOpen))
+        })
+    }
+}

assets/modules/tabs.js

@@ -0,0 +1,13 @@
+export function initTabs() {
+    document.querySelectorAll('[data-tab]').forEach(button => {
+        button.addEventListener('click', () => {
+            const targetId = button.dataset.tab
+            document.querySelectorAll('[data-tab]').forEach(b => {
+                const isActive = b.dataset.tab === targetId
+                b.style.backgroundColor = isActive ? '#111827' : 'white'
+                b.style.color = isActive ? 'white' : '#111827'
+                document.getElementById(b.dataset.tab).style.display = isActive ? 'block' : 'none'
+            })
+        })
+    })
+}