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_info_tab.dart

@@ -26,42 +26,39 @@ class DetailsInfoTab extends StatelessWidget {
       ('Favorite', item.isFavorite ? 'Yes' : 'No'),
     ];
 
-    return Scrollbar(
+    return ListView.separated(
       controller: scrollController,
-      child: ListView.separated(
-        controller: scrollController,
-        padding: const EdgeInsets.fromLTRB(20, 12, 20, 24),
-        itemCount: rows.length,
-        separatorBuilder: (context, index) => const Divider(height: 1),
-        itemBuilder: (context, index) {
-          final (label, value) = rows[index];
-          return Padding(
-            padding: const EdgeInsets.symmetric(vertical: 12),
-            child: Row(
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                SizedBox(
-                  width: 96,
-                  child: Text(
-                    label,
-                    style: theme.textTheme.bodyMedium?.copyWith(
-                      color: colorScheme.onSurfaceVariant,
-                    ),
+      padding: const EdgeInsets.fromLTRB(20, 12, 20, 24),
+      itemCount: rows.length,
+      separatorBuilder: (context, index) => const Divider(height: 1),
+      itemBuilder: (context, index) {
+        final (label, value) = rows[index];
+        return Padding(
+          padding: const EdgeInsets.symmetric(vertical: 12),
+          child: Row(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              SizedBox(
+                width: 96,
+                child: Text(
+                  label,
+                  style: theme.textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
                   ),
                 ),
-                Expanded(
-                  child: Text(
-                    value,
-                    style: theme.textTheme.bodyMedium?.copyWith(
-                      fontWeight: FontWeight.w500,
-                    ),
+              ),
+              Expanded(
+                child: Text(
+                  value,
+                  style: theme.textTheme.bodyMedium?.copyWith(
+                    fontWeight: FontWeight.w500,
                   ),
                 ),
-              ],
-            ),
-          );
-        },
-      ),
+              ),
+            ],
+          ),
+        );
+      },
     );
   }
 }