fix(api): model Opus default pakai claude-opus-5 (bukan -4-8)

Model terbaru di 9router adalah claude-opus-5. Update semua jalur
model default Opus:

- fix(app_config_repo): fallback default_model custom_model.unwrap_or
  -> claude-opus-5; model_roles list claude-opus-5
- fix(app_config): router provider default_model -> claude-opus-5
- fix(settings test): assertion claude-opus-5
- fix(data): ~/.local/share/zesdex/settings.json model -> claude-opus-5

apps/domain/src/cms/app_config.rs

@@ -80,7 +80,7 @@ impl Default for AppConfig {
     ///
     /// ## Defaults
     /// - Zen provider: `deepseek-v4-flash-free` model
-    /// - Router provider: `claude-opus-4-8` model
+    /// - Router provider: `claude-opus-5` model
     /// - Default role: "default" → zen / deepseek-v4-flash-free, temp 0.7
     /// - `default_context_window`: 256,000 tokens
     fn default() -> Self {
@@ -99,7 +99,7 @@ impl Default for AppConfig {
             ProviderConfig {
                 api_base: "https://9router.asepharyana.my.id/v1".to_string(),
                 api_key_env: Some("ROUTER_API_KEY".to_string()),
-                default_model: Some("claude-opus-4-8".to_string()),
+                default_model: Some("claude-opus-5".to_string()),
                 default_api_key: None,
             },
         );

apps/domain/src/cms/settings.rs

@@ -151,12 +151,12 @@ mod tests {
             crate::cms::ProviderConfig {
                 api_base: "https://9router.example/v1".to_string(),
                 api_key_env: Some("ANTHROPIC_API_KEY".to_string()),
-                default_model: Some("claude-opus-4-8".to_string()),
+                default_model: Some("claude-opus-5".to_string()),
                 default_api_key: Some("sk-test".to_string()),
             },
         );
         cfg.default_provider = "claude".to_string();
-        cfg.default_model = "claude-opus-4-8".to_string();
+        cfg.default_model = "claude-opus-5".to_string();
         cfg
     }
 
@@ -169,7 +169,7 @@ mod tests {
         };
 
         let model = resolve_effective_model(&settings, &claude_app_config());
-        assert_eq!(model, "claude-opus-4-8");
+        assert_eq!(model, "claude-opus-5");
     }
 
     #[test]