feat: enhance forms with decimal formatting and validation

- Updated CustomersPage.vue to use decimalString for standard discount percent.
- Enhanced IncomingInvoicesPage.vue to format item quantities, unit prices, and tax rates using decimalString.
- Improved ItemsPage.vue with new supplier price management and decimal formatting for prices.
- Modified OrganizationSetupPage.vue to use a dropdown for default tax rates and ensure numeric input for payment days.
- Updated OutgoingInvoicesPage.vue to apply decimal formatting for customer discounts and item details.
- Enhanced PriceImportsPage.vue to include additional fields in the import format.
- Improved PriceRulesPage.vue to use decimal input for markup percentages.
- Updated QuotesPage.vue to apply decimal formatting for customer discounts and item details.
- Enhanced SuppliersPage.vue to use decimal input for standard discount percent.
- Added a new SQL migration to set default unit for items to 'Stck'.
- Introduced format.ts for centralized decimal and currency formatting utilities.

backend/company-migrations/0015_activity_status_active_inactive.sql

@@ -0,0 +1,15 @@
+alter table {schema}.activities
+    drop constraint if exists activities_status_valid;
+
+update {schema}.activities
+set status = case
+    when status in ('open', 'in_progress') then 'active'
+    else 'inactive'
+end
+where status in ('open', 'in_progress', 'done', 'cancelled');
+
+alter table {schema}.activities
+    alter column status set default 'active';
+
+alter table {schema}.activities
+    add constraint activities_status_valid check (status in ('active', 'inactive'));