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/schema.ts

@@ -12,6 +12,9 @@ export const users = sqliteTable('users', {
   homeInstance: text('home_instance'),
   homeUserId: text('home_user_id'),
   replicatedInstances: text('replicated_instances').default('[]'),
+  banner: text('banner'),
+  accentColor: text('accent_color'),
+  bio: text('bio'),
   createdAt: integer('created_at').notNull(),
 });