Remove scrollbar thumb and restructure Settings profile card

- Revert the scrollbar-thumb feature entirely (per-view Scrollbar
  wrappers and the ScrollbarThemeData override) - back to plain
  scrollables with no visible thumb
- Settings: move the logout button into the profile card (next to the
  name/email), and move the ONLINE/OFFLINE badge + "Connected to..."
  text out of the top row into a combined line at the bottom of the
  card, instead of split between the AppBar and the top of the screen
- Update architecture.md/styling.md to drop the stale scrollbar-theme
  documentation

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/widgets/details/details_versions_tab.dart

@@ -118,45 +118,43 @@ class _DetailsVersionsTabState extends State<DetailsVersionsTab> {
       ..._versions,
     ];
 
-    return Scrollbar(
-      child: ListView.separated(
-        padding: const EdgeInsets.fromLTRB(20, 12, 20, 24),
-        itemCount: items.length,
-        separatorBuilder: (context, index) => const SizedBox(height: 4),
-        itemBuilder: (context, index) {
-          final version = items[index];
-          return ListTile(
-            contentPadding: EdgeInsets.zero,
-            leading: CircleAvatar(
-              backgroundColor: colorScheme.primaryContainer,
-              child: Icon(
-                Icons.history_rounded,
-                color: colorScheme.onPrimaryContainer,
-                size: 20,
-              ),
+    return ListView.separated(
+      padding: const EdgeInsets.fromLTRB(20, 12, 20, 24),
+      itemCount: items.length,
+      separatorBuilder: (context, index) => const SizedBox(height: 4),
+      itemBuilder: (context, index) {
+        final version = items[index];
+        return ListTile(
+          contentPadding: EdgeInsets.zero,
+          leading: CircleAvatar(
+            backgroundColor: colorScheme.primaryContainer,
+            child: Icon(
+              Icons.history_rounded,
+              color: colorScheme.onPrimaryContainer,
+              size: 20,
             ),
-            title: Text(
-              version.isCurrent
-                  ? 'Current version'
-                  : DateFormat.yMMMd().add_jm().format(version.timestamp),
-            ),
-            subtitle: Text(
-              '${DateFormat.yMMMd().format(version.timestamp)} • ${formatBytes(version.size)}',
-            ),
-            trailing: version.isCurrent
-                ? null
-                : PopupMenuButton<String>(
-                    onSelected: (value) => value == 'restore'
-                        ? _restore(version)
-                        : _download(version),
-                    itemBuilder: (context) => const [
-                      PopupMenuItem(value: 'restore', child: Text('Restore')),
-                      PopupMenuItem(value: 'download', child: Text('Download')),
-                    ],
-                  ),
-          );
-        },
-      ),
+          ),
+          title: Text(
+            version.isCurrent
+                ? 'Current version'
+                : DateFormat.yMMMd().add_jm().format(version.timestamp),
+          ),
+          subtitle: Text(
+            '${DateFormat.yMMMd().format(version.timestamp)} • ${formatBytes(version.size)}',
+          ),
+          trailing: version.isCurrent
+              ? null
+              : PopupMenuButton<String>(
+                  onSelected: (value) => value == 'restore'
+                      ? _restore(version)
+                      : _download(version),
+                  itemBuilder: (context) => const [
+                    PopupMenuItem(value: 'restore', child: Text('Restore')),
+                    PopupMenuItem(value: 'download', child: Text('Download')),
+                  ],
+                ),
+        );
+      },
     );
   }
 }