feat: add onboarding flow with visual redesign

Introduce 6-step onboarding screen (Goal → Gender → DOB → Height+Weight
→ Activity → Calories) with per-step accent colors, hero illustration
area (concentric circles + icon), and white card content panel.

Backend user entity and service updated to support onboarding fields
(goal, activity, height, weight, DOB, dailyCalories). Router guards
unauthenticated and onboarding-incomplete users. Profile service and
screen updated to expose language and onboarding preferences.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/features/profile/profile_screen.dart

@@ -51,12 +51,12 @@ class ProfileScreen extends ConsumerWidget {
 
 // ── Profile body ──────────────────────────────────────────────
 
-class _ProfileBody extends StatelessWidget {
+class _ProfileBody extends ConsumerWidget {
   final User user;
   const _ProfileBody({required this.user});
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     return ListView(
       padding: const EdgeInsets.fromLTRB(16, 8, 16, 32),
       children: [