fix: replace Pug language picker dropdown with native select

The old dropdown relied on data-bs-toggle and AngularJS directives,
neither of which are loaded on React-layout pages (layout-react.pug
intentionally excludes Bootstrap JS). The toggle button was inert on
pages like /user/settings.

Replace with a plain <select> that navigates via window.location.href
onchange — works without any framework on all page types.

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

services/web/app/views/layout/language-picker.pug

@@ -1,35 +1,10 @@
-include ../_mixins/material_symbol
-
-li.dropdown.dropup.subdued.language-picker(dropdown)
-	button#language-picker-toggle.btn.btn-link.btn-inline-link(
-		dropdown-toggle
-		data-ol-lang-selector-tooltip
-		data-bs-toggle='dropdown'
-		aria-haspopup='true'
-		aria-expanded='false'
-		aria-label='Select ' + translate('language')
-		tooltip=translate('language')
-		title=translate('language')
+li.language-picker
+	select.language-picker-select(
+		name='lng'
+		translate='no'
+		onchange='window.location.href="/set-language?lng="+encodeURIComponent(this.value)+"&return_to="+encodeURIComponent(window.location.pathname)'
+		aria-label=translate('select_a_language')
 	)
-		+material-symbol('translate')
-		|  
-		span.language-picker-text #{settings.translatedLanguages[currentLngCode] || currentLngCode}
-
-	ul.dropdown-menu.dropdown-menu-sm-width(
-		role='menu'
-		aria-labelledby='language-picker-toggle'
-	)
-		li.dropdown-header #{translate("language")}
 		each lngCode in availableLanguages
 			if settings.translatedLanguages[lngCode]
-				- let isActive = lngCode === currentLngCode
-				li.lng-option
-					a.menu-indent(
-						href='/set-language?lng=' + lngCode
-						role='menuitem'
-						class=['dropdown-item', {active: isActive}]
-						aria-selected=isActive ? 'true' : 'false'
-					)
-						| #{settings.translatedLanguages[lngCode]}
-						if isActive
-							+material-symbol('check', 'dropdown-item-trailing-icon')
+				option(value=lngCode selected=lngCode === currentLngCode)= settings.translatedLanguages[lngCode]