feat: add keyboard shortcut help modal triggered by ? key

src/App.tsx

@@ -8,6 +8,7 @@ import { BoardView } from "@/components/board/BoardView";
 import { CommandPalette } from "@/components/command-palette/CommandPalette";
 import { SettingsDialog } from "@/components/settings/SettingsDialog";
 import { ToastContainer } from "@/components/toast/ToastContainer";
+import { ShortcutHelpModal } from "@/components/shortcuts/ShortcutHelpModal";
 import { useKeyboardShortcuts } from "@/hooks/useKeyboardShortcuts";
 
 export default function App() {
@@ -16,6 +17,7 @@ export default function App() {
   const view = useAppStore((s) => s.view);
 
   const [settingsOpen, setSettingsOpen] = useState(false);
+  const [shortcutHelpOpen, setShortcutHelpOpen] = useState(false);
 
   useEffect(() => {
     init();
@@ -42,6 +44,16 @@ export default function App() {
     };
   }, []);
 
+  useEffect(() => {
+    function handleOpenShortcutHelp() {
+      setShortcutHelpOpen(true);
+    }
+    document.addEventListener("open-shortcut-help", handleOpenShortcutHelp);
+    return () => {
+      document.removeEventListener("open-shortcut-help", handleOpenShortcutHelp);
+    };
+  }, []);
+
   const handleOpenSettings = useCallback(() => {
     setSettingsOpen(true);
   }, []);
@@ -66,6 +78,7 @@ export default function App() {
       <CommandPalette onOpenSettings={handleOpenSettings} />
       <SettingsDialog open={settingsOpen} onOpenChange={setSettingsOpen} />
       <ToastContainer />
+      <ShortcutHelpModal open={shortcutHelpOpen} onOpenChange={setShortcutHelpOpen} />
     </>
   );
 }