feat: add featured event with automatic fallback

- Add featured_event_id to site_settings (schema + migration)
- Backend: featured event logic in /events/next/upcoming with auto-unset when event ends
- Site settings: PUT supports featuredEventId, add PUT /featured-event for admin
- Admin events: Set as featured checkbox in editor, star toggle in list, featured badge
- Admin settings: Featured Event section with current event and remove/change links
- API: siteSettingsApi.setFeaturedEvent(), Event.isFeatured, SiteSettings.featuredEventId
- Homepage/linktree unchanged: still use getNextUpcoming (now returns featured or fallback)

frontend/src/app/(public)/book/[eventId]/page.tsx

@@ -110,43 +110,12 @@ export default function BookingPage() {
 
   const [errors, setErrors] = useState<Partial<Record<keyof BookingFormData, string>>>({});
 
-  // RUC validation using modulo 11 algorithm
-  const validateRucCheckDigit = (ruc: string): boolean => {
-    const match = ruc.match(/^(\d{6,8})-(\d)$/);
-    if (!match) return false;
-    
-    const baseNumber = match[1];
-    const checkDigit = parseInt(match[2], 10);
-    
-    // Modulo 11 algorithm for Paraguayan RUC
-    const weights = [2, 3, 4, 5, 6, 7, 2, 3];
-    let sum = 0;
-    const digits = baseNumber.split('').reverse();
-    
-    for (let i = 0; i < digits.length; i++) {
-      sum += parseInt(digits[i], 10) * weights[i];
-    }
-    
-    const remainder = sum % 11;
-    const expectedCheckDigit = remainder < 2 ? 0 : 11 - remainder;
-    
-    return checkDigit === expectedCheckDigit;
-  };
+  const rucPattern = /^\d{6,10}$/;
 
-  // Format RUC input: auto-insert hyphen before last digit
+  // Format RUC input: digits only, max 10
   const formatRuc = (value: string): string => {
-    // Remove non-numeric characters
-    const digits = value.replace(/\D/g, '');
-    
-    // Limit to 9 digits (8 base + 1 check)
-    const limited = digits.slice(0, 9);
-    
-    // Auto-insert hyphen before last digit if we have more than 6 digits
-    if (limited.length > 6) {
-      return `${limited.slice(0, -1)}-${limited.slice(-1)}`;
-    }
-    
-    return limited;
+    const digits = value.replace(/\D/g, '').slice(0, 10);
+    return digits;
   };
 
   // Handle RUC input change
@@ -160,19 +129,12 @@ export default function BookingPage() {
     }
   };
 
-  // Validate RUC on blur
+  // Validate RUC on blur (optional field: 6–10 digits)
   const handleRucBlur = () => {
-    if (!formData.ruc) return; // Optional field, no validation if empty
-    
-    const rucPattern = /^[0-9]{6,8}-[0-9]{1}$/;
-    
-    if (!rucPattern.test(formData.ruc)) {
+    if (!formData.ruc) return;
+    const digits = formData.ruc.replace(/\D/g, '');
+    if (digits.length > 0 && !rucPattern.test(digits)) {
       setErrors({ ...errors, ruc: t('booking.form.errors.rucInvalidFormat') });
-      return;
-    }
-    
-    if (!validateRucCheckDigit(formData.ruc)) {
-      setErrors({ ...errors, ruc: t('booking.form.errors.rucInvalidCheckDigit') });
     }
   };
 
@@ -275,13 +237,11 @@ export default function BookingPage() {
       newErrors.phone = t('booking.form.errors.phoneTooShort');
     }
     
-    // RUC validation (optional field - only validate if filled)
+    // RUC validation (optional field - 6–10 digits if filled)
     if (formData.ruc.trim()) {
-      const rucPattern = /^[0-9]{6,8}-[0-9]{1}$/;
-      if (!rucPattern.test(formData.ruc)) {
+      const digits = formData.ruc.replace(/\D/g, '');
+      if (!/^\d{6,10}$/.test(digits)) {
         newErrors.ruc = t('booking.form.errors.rucInvalidFormat');
-      } else if (!validateRucCheckDigit(formData.ruc)) {
-        newErrors.ruc = t('booking.form.errors.rucInvalidCheckDigit');
       }
     }
     
@@ -429,7 +389,7 @@ export default function BookingPage() {
         phone: formData.phone,
         preferredLanguage: formData.preferredLanguage,
         paymentMethod: formData.paymentMethod,
-        ...(formData.ruc.trim() && { ruc: formData.ruc }),
+        ...(formData.ruc.trim() && { ruc: formData.ruc.replace(/\D/g, '') }),
         // Include attendees array for multi-ticket bookings
         ...(allAttendees.length > 1 && { attendees: allAttendees }),
       });