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.

web-frontend/src/views/PriceRulesPage.vue

@@ -3,6 +3,7 @@ import { onMounted, reactive, ref } from "vue";
 import { apiDelete, apiGet, apiPost, apiPut } from "../api";
 import FormStatus from "../components/FormStatus.vue";
 import PageHeader from "../components/PageHeader.vue";
+import { decimalString } from "../format";
 import type { PriceRule } from "../types";
 
 const rules = ref<PriceRule[]>([]);
@@ -20,7 +21,11 @@ const status = ref("");
 const kind = ref<"info" | "success" | "error">("info");
 
 function payload() {
-  return { ...form, source_id: form.source_id.trim() || null };
+  return {
+    ...form,
+    source_id: form.source_id.trim() || null,
+    markup_percent: decimalString(form.markup_percent)
+  };
 }
 
 function createNew() {
@@ -86,7 +91,7 @@ onMounted(load);
           <label class="field"><span>Name</span><input v-model="form.name" required /></label>
           <label class="field"><span>Quellentyp</span><select v-model="form.source_type"><option value="import">Import</option><option value="api">API</option><option value="supplier">Lieferant</option></select></label>
           <label class="field"><span>Quell-ID</span><input v-model="form.source_id" placeholder="optional" /></label>
-          <label class="field"><span>Aufschlag %</span><input v-model="form.markup_percent" type="number" min="-100" max="1000" step="0.0001" required /></label>
+          <label class="field"><span>Aufschlag %</span><input v-model="form.markup_percent" inputmode="decimal" required /></label>
           <label class="field"><span>Rundung</span><select v-model="form.rounding_mode"><option value="none">Keine</option><option value="cent">Cent</option><option value="five_cent">5 Cent</option><option value="ten_cent">10 Cent</option><option value="whole">Ganze Beträge</option></select></label>
           <label class="check-row"><input v-model="form.is_active" type="checkbox" /><span>Aktiv</span></label>
         </div>