feat: user profile customization with banner, accent color, bio, and full profile modal

Add banner image, accent color, and bio fields to user profiles with
full-stack support: schema migration, API validation (hex color format,
190-char bio limit), sanitizeUser propagation, and new GET /users/:id/mutuals
endpoint. Rewrite AccountPanel with live preview card, avatar/banner upload
via ImageCropModal, 16-preset accent color picker, and bio editor. Enhance
UserProfilePopout with banner display, accent-colored names, bio rendering,
and mutual counts. Add new UserProfileModal with About/Mutual Friends/Mutual
Spaces tabs and friend action buttons.

packages/server/src/db/migrate.ts

@@ -85,6 +85,14 @@ export function runMigrations(db: Database.Database): void {
       columns: [
         { name: 'banner', type: 'TEXT' }
       ]
+    },
+    {
+      name: 'users',
+      columns: [
+        { name: 'banner', type: 'TEXT' },
+        { name: 'accent_color', type: 'TEXT' },
+        { name: 'bio', type: 'TEXT' },
+      ]
     }
   ];