feat: SQL filtering, Users admin tab, dashboard polish

- Move ticket filtering from in-memory to SQL WHERE clauses
  (queue_id, status, owner use Drizzle eq/isNull; text search uses ilike;
  custom field filters use EXISTS subqueries)
- Add limit param to GET /tickets
- Add POST/PATCH/DELETE /users routes
- Add Users tab to admin page with create/edit/delete
- Smart widget positioning in dashboard (3-column grid fill)
- Show pattern hint below CF inputs in New Ticket dialog

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/lib/api.ts

@@ -95,6 +95,24 @@ export async function getUsers(): Promise<{ data: User[] | null; error: string |
   return request<User[]>("/users");
 }
 
+export async function createUser(data: {
+  username: string;
+  email?: string | null;
+}): Promise<{ data: User | null; error: string | null }> {
+  return request<User>("/users", { method: "POST", body: JSON.stringify(data) });
+}
+
+export async function updateUser(id: string, data: {
+  username?: string;
+  email?: string | null;
+}): Promise<{ data: User | null; error: string | null }> {
+  return request<User>(`/users/${id}`, { method: "PATCH", body: JSON.stringify(data) });
+}
+
+export async function deleteUser(id: string): Promise<{ data: { ok: boolean } | null; error: string | null }> {
+  return request<{ ok: boolean }>(`/users/${id}`, { method: "DELETE" });
+}
+
 export async function createQueue(data: { name: string; description?: string | null; lifecycle_id?: string | null }): Promise<{ data: Queue | null; error: string | null }> {
   return request<Queue>("/queues", { method: "POST", body: JSON.stringify(data) });
 }