feat: implement standard-compliant sidebar with comprehensive tests

Implement a new sidebar component based on DaisyUI Drawer pattern without
custom CSS variants. The sidebar supports desktop (expanded/collapsed states)
and mobile (overlay drawer) with full accessibility compliance.

Sidebar Implementation:
- Refactor sidebar component with sidebar_header, menu_item, menu_group,
  sidebar_footer sub-components
- Add logo (mila.svg) with size-8 (32px) always visible
- Implement toggle button with icon swap (chevron-left/right) for desktop
- Add nested menu support with details/summary (expanded) and dropdown
  (collapsed) patterns
- Implement footer with language selector (expanded-only), theme toggle,
  and user menu with avatar
- Update layouts.ex to use drawer pattern with data-sidebar-expanded
  attribute for state management

CSS & JavaScript:
- Add CSS styles for sidebar state management via data-attribute selectors
- Implement SidebarState JavaScript hook for localStorage persistence
- Add smooth width transitions (w-64 ↔ w-16) for desktop collapsed state
- Add CSS classes for expanded-only, menu-label, and icon visibility

Documentation:
- Add sidebar-analysis-current-state.md: Analysis of current implementation
- Add sidebar-requirements-v2.md: Complete specification for new sidebar
- Add daisyui-drawer-pattern.md: DaisyUI pattern documentation
- Add umsetzung-sidebar.md: Step-by-step implementation guide

Testing:
- Add comprehensive component tests for all sidebar sub-components
- Add integration tests for sidebar state management and mobile drawer
- Extend accessibility tests (ARIA labels, roles, keyboard navigation)
- Add regression tests for duplicate IDs, hover effects, and tooltips
- Ensure full test coverage per specification requirements

lib/mv_web/components/layouts.ex

@@ -9,7 +9,6 @@ defmodule MvWeb.Layouts do
   """
   use MvWeb, :html
   use Gettext, backend: MvWeb.Gettext
-  import MvWeb.Layouts.Navbar
   import MvWeb.Layouts.Sidebar
 
   embed_templates "layouts/*"
@@ -44,21 +43,39 @@ defmodule MvWeb.Layouts do
     assigns = assign(assigns, :club_name, club_name)
 
     ~H"""
-    <div class="drawer">
-      <input id="main-drawer" type="checkbox" class="drawer-toggle" />
-      <div class="drawer-content">
-        <%= if @current_user do %>
-          <.navbar current_user={@current_user} />
-        <% end %>
-        <main class="px-4 py-20 sm:px-6 lg:px-16">
-          <div class="mx-auto space-y-4 max-full">
-            {render_slot(@inner_block)}
-          </div>
-        </main>
-      </div>
+    <%= if @current_user do %>
+      <div id="app-layout" class="drawer lg:drawer-open" data-sidebar-expanded="true" phx-hook="SidebarState">
+        <input id="mobile-drawer" type="checkbox" class="drawer-toggle" />
 
-      <.sidebar current_user={@current_user} club_name={@club_name} />
-    </div>
+        <div class="drawer-content flex flex-col relative z-0">
+          <!-- Mobile Header (only visible on mobile) -->
+          <header class="lg:hidden sticky top-0 z-10 navbar bg-base-100 shadow-sm">
+            <label for="mobile-drawer" class="btn btn-square btn-ghost" aria-label={gettext("Open navigation menu")}>
+              <.icon name="hero-bars-3" class="size-6" aria-hidden="true" />
+            </label>
+            <span class="font-bold">{@club_name}</span>
+          </header>
+
+          <!-- Main Content (shared between mobile and desktop) -->
+          <main class="px-4 py-8 sm:px-6 lg:px-8">
+            <div class="mx-auto space-y-4 max-full">
+              {render_slot(@inner_block)}
+            </div>
+          </main>
+        </div>
+
+        <div class="drawer-side z-40">
+          <.sidebar current_user={@current_user} club_name={@club_name} mobile={false} />
+        </div>
+      </div>
+    <% else %>
+      <!-- Not logged in -->
+      <main class="px-4 py-8 sm:px-6">
+        <div class="mx-auto space-y-4 max-full">
+          {render_slot(@inner_block)}
+        </div>
+      </main>
+    <% end %>
 
     <.flash_group flash={@flash} />
     """