refactor(backend): alihkan Settings ke zesdex-cms JsonSettingsRepository

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

crates/zesdex-backend/src/app/runtime/context/window.rs

@@ -6,7 +6,7 @@
 //! displayed "?" on no match instead of falling back like the other two,
 //! an inconsistency this unifies away).
 use crate::model::app_config::AppConfig;
-use crate::model::settings::Settings;
+use zesdex_cms::domain::settings::Settings;
 
 /// Resolve the context-window size (in tokens) for the currently
 /// configured provider/model.