feat(52-mobile-main-menu): hamburger + slide-in overlay sidebar na mobile

Zastapienie niedzialajacej nawigacji horyzontalnej pelnoekranowym
overlay sidebar z hamburgerem, backdrop i animacja CSS transform.

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

resources/scss/app.scss

@@ -2251,37 +2251,85 @@ h4.section-title {
   color: #334155;
 }
 
+// Hamburger button (hidden on desktop)
+.topbar__hamburger {
+  display: none;
+  align-items: center;
+  justify-content: center;
+  width: 36px;
+  height: 36px;
+  padding: 0;
+  background: transparent;
+  border: none;
+  color: var(--c-text-strong);
+  cursor: pointer;
+  border-radius: 6px;
+  flex-shrink: 0;
+
+  &:hover {
+    background: var(--c-bg-subtle, #f1f5f9);
+  }
+}
+
+// Mobile backdrop overlay
+.sidebar-backdrop {
+  display: none;
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.5);
+  z-index: 999;
+  opacity: 0;
+  transition: opacity 0.25s ease;
+
+  &.is-visible {
+    display: block;
+    opacity: 1;
+  }
+}
+
+// Body scroll lock
+body.no-scroll {
+  overflow: hidden;
+}
+
 @media (max-width: 768px) {
-  .app-shell {
-    flex-direction: column;
+  .topbar__hamburger {
+    display: flex;
   }
 
   .sidebar {
-    width: 100% !important;
-    min-width: 0 !important;
-    border-right: 0;
-    border-bottom: 1px solid #243041;
-    padding: 14px;
-    overflow-x: auto;
+    position: fixed;
+    top: 0;
+    left: 0;
+    bottom: 0;
+    width: 280px;
+    min-width: 280px;
+    z-index: 1000;
+    transform: translateX(-100%);
+    transition: transform 0.25s ease;
+    border-right: 1px solid #243041;
+    overflow-y: auto;
+
+    &.is-mobile-open {
+      transform: translateX(0);
+    }
   }
 
   .sidebar__brand {
-    margin: 0 0 10px;
-    font-size: 22px;
+    margin: 4px 4px 12px;
   }
 
   .sidebar__collapse-btn {
-    display: none;
+    display: flex;
+  }
+
+  .sidebar__collapse-icon {
+    transform: rotate(180deg);
   }
 
   .sidebar__nav {
-    display: flex;
-    gap: 8px;
-    overflow-x: auto;
-  }
-
-  .sidebar__link {
-    white-space: nowrap;
+    display: grid;
+    gap: 4px;
   }
 
   .topbar {