feat: add team selector to dashboard page header

- Dropdown to assign/unassign dashboard to a team
- Updates immediately via PATCH
- createDashboard and updateDashboard API now accept team_id

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

web/src/lib/api.ts

@@ -297,6 +297,7 @@ export async function getDashboard(id: string): Promise<{ data: Dashboard | null
 export async function createDashboard(data: {
   name: string;
   description?: string;
+  team_id?: string | null;
   is_default?: boolean;
 }): Promise<{ data: Dashboard | null; error: string | null }> {
   return request<Dashboard>("/dashboards", { method: "POST", body: JSON.stringify(data) });
@@ -305,6 +306,7 @@ export async function createDashboard(data: {
 export async function updateDashboard(id: string, data: {
   name?: string;
   description?: string | null;
+  team_id?: string | null;
   is_default?: boolean;
   layout?: unknown[];
 }): Promise<{ data: Dashboard | null; error: string | null }> {