feat: explore tab, React Query data layer, programs, sync, analytics, testing infrastructure

- Replace browse tab with Supabase-connected explore tab with filters
- Add React Query for data fetching with loading states
- Add 3 structured programs with weekly progression
- Add Supabase anonymous auth sync service
- Add PostHog analytics with screen tracking and events
- Add comprehensive test strategy (Vitest + Maestro E2E)
- Add RevenueCat subscription system with DEV simulation
- Add i18n translations for new screens (EN/FR/DE/ES)
- Add data deletion modal, sync consent modal
- Add assessment screen and program routes
- Add GitHub Actions CI workflow
- Update activity store with sync integration

app/_layout.tsx

@@ -134,6 +134,12 @@ function RootLayoutInner() {
                 animation: 'slide_from_right',
               }}
             />
+            <Stack.Screen
+              name="assessment"
+              options={{
+                animation: 'slide_from_right',
+              }}
+            />
             <Stack.Screen
               name="player/[id]"
               options={{