Add keyboard navigation: e/c/slash shortcuts, j/k list nav, focus visibility

- App.vue: e → edit on viewer pages; / → focus search (custom event); c → focus
  chat on home or navigate to /chat; update shortcuts panel with Lists + Chat sections
- theme.css: add a:focus-visible to focus-ring rules (router-link cards now show
  visible keyboard focus outline)
- SearchBar.vue: expose focus() via defineExpose for cross-component focus dispatch
- NotesListView / TasksListView: j/k vim-style navigation with kb-active-item
  highlight; listen for shortcut:focus-search; cleanup on unmount
- HomeView.vue: listen for shortcut:focus-chat, call chatInputRef.focus()

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

frontend/src/App.vue

@@ -95,6 +95,24 @@ function onGlobalKeydown(e: KeyboardEvent) {
     case "t":
       router.push("/tasks/new");
       break;
+    case "e": {
+      const name = router.currentRoute.value.name;
+      if (name === "note-view" || name === "task-view") {
+        router.push(router.currentRoute.value.path + "/edit");
+      }
+      break;
+    }
+    case "/":
+      e.preventDefault();
+      document.dispatchEvent(new CustomEvent("shortcut:focus-search"));
+      break;
+    case "c":
+      if (router.currentRoute.value.name === "home") {
+        document.dispatchEvent(new CustomEvent("shortcut:focus-chat"));
+      } else {
+        router.push("/chat");
+      }
+      break;
   }
 }
 
@@ -193,8 +211,33 @@ onUnmounted(() => {
                 <span class="shortcut-desc">New task</span>
               </div>
             </div>
+            <div class="shortcuts-section">
+              <div class="shortcuts-section-title">Lists</div>
+              <div class="shortcut-row">
+                <kbd class="shortcut-key">/</kbd>
+                <span class="shortcut-desc">Focus search bar</span>
+              </div>
+              <div class="shortcut-row">
+                <kbd class="shortcut-key">j</kbd>
+                <span class="shortcut-key-sep">/</span>
+                <kbd class="shortcut-key">k</kbd>
+                <span class="shortcut-desc">Move down / up</span>
+              </div>
+              <div class="shortcut-row">
+                <kbd class="shortcut-key">Enter</kbd>
+                <span class="shortcut-desc">Open selected item</span>
+              </div>
+              <div class="shortcut-row">
+                <kbd class="shortcut-key">e</kbd>
+                <span class="shortcut-desc">Edit current item (viewer)</span>
+              </div>
+            </div>
             <div class="shortcuts-section">
               <div class="shortcuts-section-title">Chat</div>
+              <div class="shortcut-row">
+                <kbd class="shortcut-key">c</kbd>
+                <span class="shortcut-desc">Focus chat (home) / go to chat</span>
+              </div>
               <div class="shortcut-row">
                 <kbd class="shortcut-key">Enter</kbd>
                 <span class="shortcut-desc">Send message</span>