feat: full onboarding + quiz flow (Flutter from scratch)

- splash → intro → 5-step quiz → result screen
- Plus Jakarta Sans typography, indigo brand system
- animated quiz rows, multi-select concerns, progress bar
- Shaynee mascot reveal on result screen only
- flutter_animate for all transitions

lib/theme.dart

@@ -0,0 +1,43 @@
+import 'package:flutter/material.dart';
+import 'package:google_fonts/google_fonts.dart';
+
+class SColors {
+  static const primary = Color(0xFF5B4FCF);
+  static const primaryLight = Color(0xFF7B70E0);
+  static const primaryDeep = Color(0xFF3D32A8);
+  static const accent = Color(0xFFFF7EB3);
+  static const accentSoft = Color(0xFFFFF0F6);
+  static const bgPage = Color(0xFFFAF9FF);
+  static const surface = Color(0xFFFFFFFF);
+  static const textPrimary = Color(0xFF1C1A2E);
+  static const textSecondary = Color(0xFF7B7A8E);
+  static const border = Color(0xFFE8E6F0);
+  static const skyTint = Color(0xFFEEECFA);
+  static const gradientTop = Color(0xFF5B4FCF);
+  static const gradientBot = Color(0xFF8B5CF6);
+}
+
+ThemeData buildTheme() {
+  return ThemeData(
+    colorScheme: ColorScheme.fromSeed(
+      seedColor: SColors.primary,
+      brightness: Brightness.light,
+    ),
+    scaffoldBackgroundColor: SColors.bgPage,
+    textTheme: GoogleFonts.plusJakartaSansTextTheme().copyWith(
+      displayLarge: GoogleFonts.plusJakartaSans(
+        fontSize: 32, fontWeight: FontWeight.w800, color: SColors.textPrimary,
+      ),
+      headlineMedium: GoogleFonts.plusJakartaSans(
+        fontSize: 24, fontWeight: FontWeight.w700, color: SColors.textPrimary,
+      ),
+      bodyLarge: GoogleFonts.plusJakartaSans(
+        fontSize: 16, fontWeight: FontWeight.w400, color: SColors.textPrimary,
+      ),
+      bodyMedium: GoogleFonts.plusJakartaSans(
+        fontSize: 14, fontWeight: FontWeight.w400, color: SColors.textSecondary,
+      ),
+    ),
+    useMaterial3: true,
+  );
+}