feat(mobile): add onboarding tour for voting page

- Add OnboardingTour component with step-by-step guidance
- Add useOnboarding composable for state management
- Reset onboarding on logout for re-viewing
- 4 steps: welcome, award selection, program voting, progress

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/client-mobile/src/composables/useOnboarding.ts

@@ -0,0 +1,64 @@
+import { ref, computed } from 'vue';
+
+export interface TourStep {
+  target?: string;
+  title?: string;
+  content: string;
+  position?: 'top' | 'bottom' | 'left' | 'right' | 'center';
+}
+
+const STORAGE_KEY = 'gala_onboarding_completed';
+
+// Shared state across components
+const isCompleted = ref(localStorage.getItem(STORAGE_KEY) === 'true');
+const showTour = ref(false);
+const currentStep = ref(0);
+
+export function useOnboarding() {
+  const shouldShowTour = computed(() => !isCompleted.value);
+
+  function start() {
+    if (isCompleted.value) return;
+    currentStep.value = 0;
+    showTour.value = true;
+  }
+
+  function next() {
+    currentStep.value++;
+  }
+
+  function prev() {
+    if (currentStep.value > 0) {
+      currentStep.value--;
+    }
+  }
+
+  function skip() {
+    complete();
+  }
+
+  function complete() {
+    showTour.value = false;
+    isCompleted.value = true;
+    localStorage.setItem(STORAGE_KEY, 'true');
+  }
+
+  function reset() {
+    localStorage.removeItem(STORAGE_KEY);
+    isCompleted.value = false;
+    currentStep.value = 0;
+  }
+
+  return {
+    isCompleted,
+    showTour,
+    currentStep,
+    shouldShowTour,
+    start,
+    next,
+    prev,
+    skip,
+    complete,
+    reset,
+  };
+}