refactor(api): reorder imports and update code formatting across repository endpoints

- Reordered actix-web imports to standardize import order
- Reordered crate module imports to follow alphabetical ordering
- Updated function calls to use multi-line formatting for better readability
- Standardized blank lines around documentation comments
- Applied consistent formatting to response handling methods
- Normalized import organization across all repository-related API files
- Improved code consistency and maintainability through standardized formatting
- Applied formatting updates to all repository endpoint implementations

api/user/update_appearance.rs

@@ -0,0 +1,56 @@
+use actix_web::{HttpResponse, web};
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::models::users::UserAppearance;
+use crate::service::AppService;
+use crate::service::user::appearance::UpdateUserAppearanceParams;
+use crate::session::Session;
+
+/// Update user appearance settings
+///
+/// Updates the authenticated user's UI appearance preferences.
+/// Requires authentication.
+///
+/// Updatable fields:
+/// - theme: UI theme ("system", "light", "dark")
+/// - color_scheme: Color scheme ("system", "light", "dark")
+/// - density: UI density ("compact", "comfortable")
+/// - font_size: Font size ("small", "medium", "large")
+/// - editor_theme: Code editor theme name
+/// - markdown_preview: Enable/disable markdown live preview
+/// - reduced_motion: Enable/disable reduced motion
+///
+/// All fields are optional; only provided fields are updated.
+/// Returns the updated appearance settings.
+#[utoipa::path(
+    put,
+    path = "/api/v1/user/appearance",
+    tag = "User",
+    operation_id = "userUpdateAppearance",
+    request_body(
+        content = UpdateUserAppearanceParams,
+        description = "Appearance update parameters (all fields optional)",
+        content_type = "application/json"
+    ),
+    responses(
+        (status = 200, description = "Appearance settings updated successfully. Returns all updated UI preferences.", body = ApiResponse<UserAppearance>),
+        (status = 400, description = "Invalid parameters: unsupported theme, color scheme, density, or font size", body = ApiErrorResponse),
+        (status = 401, description = "Authentication required or session expired", body = ApiErrorResponse),
+        (status = 500, description = "Internal server error", body = ApiErrorResponse),
+    ),
+    security(
+        ("session_cookie" = [])
+    )
+)]
+pub async fn update_appearance(
+    service: web::Data<AppService>,
+    session: Session,
+    params: web::Json<UpdateUserAppearanceParams>,
+) -> Result<HttpResponse, AppError> {
+    let appearance = service
+        .user
+        .user_update_appearance(&session, params.into_inner())
+        .await?;
+    Ok(HttpResponse::Ok().json(ApiResponse::new(appearance)))
+}