Add admin users, BYOC teams, hosts schema, and Redis for host registration

Introduce three migrations: admin permissions (is_admin + permissions table),
BYOC team tracking, and multi-host support (hosts, host_tokens, host_tags).
Add Redis to dev infra and wire up client in control plane for ephemeral
host registration tokens. Add go-redis dependency.

db/queries/users.sql

@@ -13,3 +13,24 @@ SELECT * FROM users WHERE id = $1;
 INSERT INTO users (id, email)
 VALUES ($1, $2)
 RETURNING *;
+
+-- name: SetUserAdmin :exec
+UPDATE users SET is_admin = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: GetAdminUsers :many
+SELECT * FROM users WHERE is_admin = TRUE ORDER BY created_at;
+
+-- name: InsertAdminPermission :exec
+INSERT INTO admin_permissions (id, user_id, permission)
+VALUES ($1, $2, $3);
+
+-- name: DeleteAdminPermission :exec
+DELETE FROM admin_permissions WHERE user_id = $1 AND permission = $2;
+
+-- name: GetAdminPermissions :many
+SELECT * FROM admin_permissions WHERE user_id = $1 ORDER BY permission;
+
+-- name: HasAdminPermission :one
+SELECT EXISTS(
+    SELECT 1 FROM admin_permissions WHERE user_id = $1 AND permission = $2
+) AS has_permission;