feat(web): settings to keep the search open and hide home pickers; collapsible menu sections

- appearance settings get "collapse search" (off keeps the field always open)
  and separate switches for the activity and mood pickers on the home page;
  stored in ui_prefs (search_collapse, home_activities, home_moods)
- Collection and Admin headers in the sidebar fold their items; the state is
  remembered in the browser, a folded Admin shows the review queue badge;
  icon-only and phone layouts always show every item

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/widgets/AppShell.module.css

@@ -118,12 +118,52 @@
 }
 
 .navSection {
-  margin: 18px 12px 6px;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  margin: 12px 0 2px;
+  padding: 6px 12px;
+  border: 0;
+  border-radius: 8px;
+  background: none;
+  font: inherit;
   font-size: 11px;
   font-weight: 700;
   letter-spacing: 0.08em;
   text-transform: uppercase;
   color: var(--text3);
+  text-align: left;
+  cursor: pointer;
+}
+
+.navSection:hover {
+  color: var(--text2);
+}
+
+.navSection:focus-visible {
+  outline: 2px solid var(--accent);
+  outline-offset: -2px;
+}
+
+.navSectionTitle {
+  flex: 1;
+}
+
+.navChevron {
+  transition: transform 0.2s;
+}
+
+.navChevronOpen {
+  transform: rotate(90deg);
+}
+
+/* Обёртка не мешает раскладке: пункты остаются детьми .side (на телефоне это нижняя панель). */
+.navGroup {
+  display: contents;
+}
+
+.navGroupFolded {
+  display: none;
 }
 
 .navItem {
@@ -209,9 +249,19 @@
 
   .navSection {
     margin: 14px 0 6px;
-    text-align: center;
-    font-size: 0;
+    padding: 0;
+    border-radius: 0;
     border-top: 1px solid var(--line);
+    pointer-events: none;
+  }
+
+  .navSection > * {
+    display: none;
+  }
+
+  /* Без подписей свернуть раздел нельзя — пункты видны всегда. */
+  .navGroupFolded {
+    display: contents;
   }
 }