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/utils/sanitize.ts

@@ -16,6 +16,9 @@ export function sanitizeUser(row: typeof schema.users.$inferSelect): User {
     username: row.username,
     displayName: row.displayName,
     avatar: row.avatar,
+    banner: row.banner ?? null,
+    accentColor: row.accentColor ?? null,
+    bio: row.bio ?? null,
     status: (row.status ?? 'offline') as User['status'],
     customStatus: row.customStatus,
     isAdmin: row.isAdmin === 1,