feat(member): account/profile polish + tier upgrade flow

- Timezone: curated USelectMenu dropdown (app/config/timezones.js), preserves unknown saved values
- Profile save now uses useToast() for success/error; remove inline save banner
- Nav onboarding dot nudged down 1px for optical alignment with lowercase text
- Onboarding: skip a suggestion with POST /api/onboarding/track {skip}; member.onboarding.skipped map; does not affect graduation
- CirclePicker takes :saved-value so 'Current' badge stays until save completes
- PrivacyToggle is binary (USwitch labeled Private); member schema enum reduced to ['members','private']; zod coerces legacy 'public'
- New /member/payment-setup page: HelcimPay $0 verify + update-contribution, wired from account.vue via requiresPaymentSetup redirect
- Helcim portal: NUXT_PUBLIC_HELCIM_PORTAL_URL env + account.vue 'Manage billing in Helcim' link
- Migration script: scripts/migrate-privacy-public-to-members.js

app/components/AppNavigation.vue

@@ -339,5 +339,6 @@ const exploreItems = [
   background: var(--candle);
   margin-left: 6px;
   vertical-align: middle;
+  transform: translateY(-1px);
 }
 </style>