feat: Add Pro features discovery banner

Adds a dismissible banner in the topbar that informs users about
PLANKA Pro features.

- Dismissible per-user (stored in localStorage)
- Reappears after 30 days
- Rotates between main message and 3 feature highlights
- Links to planka.app/pro (with ref parameter for anonymous source attribution)

client/src/locales/id-ID/core.js

@@ -145,6 +145,13 @@ export default {
       customFieldGroups_title: 'Grup bidang kustom',
       customField_title: 'Bidang kustom',
       customFields_title: 'Bidang kustom',
+      discoverPlankaPro: '✨ Lebih banyak fitur untuk papan Anda: Temukan PLANKA Pro',
+      discoverPlankaPro_title: 'Temukan PLANKA Pro',
+      upgradeTeamToPro_title: 'Tingkatkan tim ke Pro',
+      proFeatureCalendar: '✨ Tampilan Kalender untuk papan Anda',
+      proFeatureRecurringCards: '✨ Kartu Berulang & Otomatisasi',
+      proFeatureGuestRoles: '✨ Peran Tamu & Kolaborasi Eksternal',
+      dismissProBannerFor30Days: 'Tutup selama 30 hari',
       customerPanel_title: 'Panel pelanggan',
       dangerZone_title: 'Zona berbahaya',
       date: 'Tanggal',