feat: require updateScope selection and improve form UX

Location Edit Form:
- Add validation requiring user to select update scope when editing locations
- Add "no-scope-selected" as placeholder option that must be replaced with valid choice
- Display validation error if user attempts to submit without selecting scope
- Clarify update scope options with improved wording (e.g., "ALL months (past and future)")

Bill Form UX:
- Add emoji icons (👤 tenant, 🔑 landlord) to "who bears cost" options for visual clarity

Translation updates:
- Add "update-scope-required" validation message (EN/HR)
- Improve clarity of update scope option labels
- Standardize Croatian terminology ("zadani" instead of "trenutni" for current month)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

web-app/messages/en.json

@@ -138,8 +138,8 @@
     "attachment": "Attachment",
     "back-button": "Back",
     "billed-to-legend": "Who bears the cost?",
-    "billed-to-tenant-option": "the tenant bears this cost",
-    "billed-to-landlord-option": "the landlord bears this cost",
+    "billed-to-tenant-option": "👤 the tenant bears this cost",
+    "billed-to-landlord-option": "🔑 the landlord bears this cost",
     "billed-to-info": "This option is intended for cases where part of the utility costs are not charged to the tenant. If 'the landlord bears this cost' is selected, this bill will not be included in the monthly statement shown to the tenant.",
     "upload-proof-of-payment-legend": "Proof of payment",
     "upload-proof-of-payment-label": "Here you can upload proof of payment:"
@@ -209,13 +209,14 @@
     "save-button": "Save",
     "cancel-button": "Cancel",
     "delete-tooltip": "Delete realestate",
-    "scope-legend": "Scope of changes",
+    "scope-legend": "Update scope",
     "add-to-subsequent-months": "add to all subsequent months",
     "update-scope-info": "Location records for each month are stored separately. Please choose which records you want to update.",
     "update-scope-legend": "I want to update the following records:",
+    "update-option-placeholder": "👉 choose one of available options",
     "update-current-month": "current month only",
     "update-subsequent-months": "current and all future months",
-    "update-all-months": "all months",
+    "update-all-months": "ALL months (past and future)",
     "validation": {
       "location-name-required": "Relaestate name is required",
       "tenant-name-required": "tenant name is missing",
@@ -226,6 +227,7 @@
       "rent-amount-required": "rent amount is required when rent notification is enabled",
       "rent-amount-integer": "rent amount must be a whole number (no decimal places)",
       "rent-amount-positive": "rent amount must be a positive number",
+      "update-scope-required": "please select which records to update",
       "validation-failed": "Validation failed. Please check the form and try again."
     }
   },