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/sv-SE/core.js

@@ -149,6 +149,13 @@ export default {
       customFieldGroups_title: 'Anpassade fältgrupper',
       customField_title: 'Anpassat fält',
       customFields_title: 'Anpassade fält',
+      discoverPlankaPro: '✨ Fler funktioner för dina bräden: Upptäck PLANKA Pro',
+      discoverPlankaPro_title: 'Upptäck PLANKA Pro',
+      upgradeTeamToPro_title: 'Uppgradera teamet till Pro',
+      proFeatureCalendar: '✨ Kalendervy för dina bräden',
+      proFeatureRecurringCards: '✨ Återkommande kort och automatisering',
+      proFeatureGuestRoles: '✨ Gästroller och externt samarbete',
+      dismissProBannerFor30Days: 'Stäng i 30 dagar',
       customerPanel_title: 'Kundpanel',
       dangerZone_title: 'Farozon',
       date: 'Datum',