swarm-ui: set the review classifier's keys from the classifier settings

The classifier's Anthropic and ACP provider keys were written by hand in the
secret store's UI. The controller now stores them: GET
/api/review-classifier/keys says whether each is set and when it changed, and
PUT /api/review-classifier/keys/{runtime} writes one. No route answers a key.

The controller's store policy gains create and update on the two leaves with
no read of their values, and a metadata read for the set state. The swarm UI's
classifier settings card gets a key form beside the settings, saved apart
because it goes to the secret store.

swarm-controller/src/review_classifier.rs

@@ -40,6 +40,7 @@ use self::settings::{Settings, SettingsSource};
 use crate::forge::{self, DefaultBranchFiles, PullForReview};
 use crate::routes::{AppState, error_problem};
 
+pub(crate) mod keys;
 pub(crate) mod metrics;
 pub(crate) mod open_pr;
 pub(crate) mod review;