feat(sidebar): Notion-style collapse/peek, desktop reopen button, Ctrl+\\ toggle

Stop collapsing the sidebar on navigation (was hiding the nav when opening Shared pages). Show the hamburger in the top-left on desktop when collapsed, add a left-edge hover zone that floats the sidebar in and auto-collapses on mouse leave, and bind Ctrl/Cmd+\\ to toggle it.

static/js/app.js

@@ -325,6 +325,14 @@
     fdLoad(window.location.href, false);
   });
 
+  // Ctrl/Cmd + \ : toggle the sidebar (Notion-style).
+  document.addEventListener('keydown', function(e) {
+    if ((e.ctrlKey || e.metaKey) && (e.key === '\\' || e.code === 'Backslash')) {
+      e.preventDefault();
+      document.dispatchEvent(new CustomEvent('fd-toggle-sidebar'));
+    }
+  });
+
   // Programmatic navigation used by Alpine helpers.
   window.fdNavigate = function(url, opts) {
     opts = opts || {};
@@ -379,7 +387,7 @@
       var doc = new DOMParser().parseFromString(d.serverResponse, 'text/html');
       var mw = doc.querySelector('.main-wrapper');
       if (mw) d.serverResponse = mw.outerHTML;
-    } catch (e) { /* keep original response on parse failure */ }
+    } catch { /* keep original response on parse failure */ }
   });
 
   document.body.addEventListener('htmx:afterSwap', function(evt) {