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/Tickets.tsx

@@ -154,7 +154,7 @@ export default function Tickets() {
   const currentFilters = useMemo(
     () => ({
       status: status || undefined,
-      severity: severity || undefined,
+      severity: severity ? Number(severity) : undefined,
       assigneeId: assigneeId || undefined,
       categoryId: categoryId || undefined,
       typeId: typeId || undefined,