refactor(backend): alihkan AppConfig ke zesdex-cms JsonAppConfigRepository

Semua pemanggilan AppConfig::load() diganti dengan
JsonAppConfigRepository + AppConfigRepository trait.
Re-export model::app_config dihapus dari model/mod.rs.

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

crates/zesdex-backend/src/app/state/rest.rs

@@ -15,10 +15,12 @@ use super::types::{Origin, Toast, TranscriptCache};
 use crate::app::lsp::LspManager;
 use crate::app::mcp::manager::McpManager;
 use crate::app::workflow::engine::WorkflowEngine;
-use crate::model::app_config::AppConfig;
 use crate::model::editlog::EditLog;
+use zesdex_cms::domain::app_config::AppConfig;
+use zesdex_cms::domain::repository::AppConfigRepository;
 use zesdex_cms::domain::repository::SettingsRepository;
 use zesdex_cms::domain::settings::Settings;
+use zesdex_cms::infrastructure::persistence::app_config_repo::JsonAppConfigRepository;
 use zesdex_cms::infrastructure::persistence::settings_repo::JsonSettingsRepository;
 
 /// A single transcript entry rendered in the TUI chat pane.
@@ -92,7 +94,9 @@ impl AppStateRest {
         let settings = JsonSettingsRepository::new()
             .load(&store_base_dir)
             .unwrap_or_default();
-        let app_config = AppConfig::load();
+        let app_config = JsonAppConfigRepository::new()
+            .load(&store_base_dir)
+            .unwrap_or_default();
         let worktrees_dir = memory_dir.parent().unwrap_or_else(|| {
             tracing::warn!("[state] memory_dir '{}' has no parent, using it for worktrees", memory_dir.display());
             &memory_dir