Type mutation inputs with shared Zod schemas instead of Record<string, unknown>

Replaced loose Record<string, unknown> types on useCreateTicket,
useUpdateTicket, useCreateUser, useUpdateUser, useUpdateWebhook,
and useCreateSavedView with their corresponding shared schema types.
Fixed three type errors this surfaced at call sites.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/pages/NewTicket.tsx

@@ -38,9 +38,10 @@ export default function NewTicketModal({ onClose }: NewTicketModalProps) {
   const onSubmit = async (data: CreateTicketInput) => {
     setError('');
     try {
-      const payload: Record<string, unknown> = { ...data };
-      if (!data.assigneeId) delete payload.assigneeId;
-      const created = await createTicket.mutateAsync(payload);
+      const { assigneeId, ...rest } = data;
+      const created = await createTicket.mutateAsync(
+        assigneeId ? { ...rest, assigneeId } : rest,
+      );
       onClose();
       navigate(`/${created.displayId}`);
     } catch {