Admin Users: show each user's org and move a user into yours

A viewer whose first login ran self-serve signup got an empty org of
their own (org_role owner), so they saw no incidents or calls, and the
earlier fix deliberately never moved a user who already had an org.
PATCH /admin/users/{uid} now moves a user when org_id is passed
explicitly (claims + org_members, audited with left_org_id; the old org
is not deleted). The user list returns org_id/org_role, and the admin
user panel shows the org and a 'Move to my organization' button when it
isn't yours.

Verified: c2-core pytest 496 passed; frontend tsc --noEmit clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/lib/c2api.ts

@@ -328,7 +328,10 @@ export const c2api = {
     }),
   getUser: (uid: string) =>
     request<import("@/lib/types").UserRecord>(`/admin/users/${uid}`),
-  updateUser: (uid: string, body: { role?: string; owned_node_ids?: string[]; display_name?: string }) =>
+  updateUser: (
+    uid: string,
+    body: { role?: string; owned_node_ids?: string[]; display_name?: string; org_id?: string },
+  ) =>
     request<import("@/lib/types").UserRecord>(`/admin/users/${uid}`, {
       method: "PATCH",
       body: JSON.stringify(body),