fix: update client_or_provider default value and improve error handling in form submission

frontend/src/routes/dashboard/clients_and_providers/edit/[[id]]/+page.svelte

@@ -49,7 +49,7 @@
 		name: '',
 		short_name: '',
 		curp: '',
-		client_or_provider: 'client',
+		client_or_provider: 'both',
 		type_nat_foreign: 'N',
 		responsible: '',
 		position: '',
@@ -224,7 +224,7 @@
 		} catch (e: any) {
 			console.error(e);
 			error = e.message || 'Error al guardar';
-			toast.error(error);
+			toast.error(error || 'Error al guardar');
 		} finally {
 			loading = false;
 		}
@@ -314,7 +314,11 @@
 								</div>
 								<div class="grid gap-2">
 									<Label for="type">Tipo de Relación <span class="text-destructive">*</span></Label>
-									<Select.Root type="single" bind:value={formData.client_or_provider}>
+								<Select.Root
+									type="single"
+									value={formData.client_or_provider}
+									onValueChange={(v) => (formData.client_or_provider = v)}
+								>
 										<Select.Trigger id="type">
 											{typeLabels[formData.client_or_provider] || 'Selecciona un tipo'}
 										</Select.Trigger>
@@ -357,7 +361,11 @@
 								</div>
 								<div class="grid gap-2">
 									<Label for="type_nat">Tipo Origen</Label>
-									<Select.Root type="single" bind:value={formData.type_nat_foreign}>
+								<Select.Root
+									type="single"
+									value={formData.type_nat_foreign}
+									onValueChange={(v) => (formData.type_nat_foreign = v)}
+								>
 										<Select.Trigger id="type_nat">
 											{formData.type_nat_foreign === 'N'
 												? 'Nacional'