refactor(workspace): pass workspace object instead of id to service methods

- Replace workspace_id parameter with Workspace object reference in all workspace service methods
- Remove redundant find_workspace_by_id calls that were duplicated in each method
- Update all method signatures across approval, audit, billing, branding, core, settings and stats modules
- Modify SQL queries to bind ws.id instead of separate workspace_id parameter
- Add Workspace import to all affected modules
- Adjust method calls in API handlers to pass workspace object instead of id
- Consolidate workspace retrieval logic to single location per operation flow

api/workspace/list.rs

@@ -0,0 +1,44 @@
+use actix_web::{HttpResponse, web};
+use serde::Deserialize;
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::models::workspaces::Workspace;
+use crate::service::AppService;
+use crate::session::Session;
+
+#[derive(Deserialize, utoipa::IntoParams)]
+pub struct ListQuery {
+    pub limit: Option<i64>,
+    pub offset: Option<i64>,
+}
+
+#[utoipa::path(
+    get,
+    path = "/api/v1/workspaces",
+    tag = "Workspaces",
+    operation_id = "workspaceList",
+    summary = "List accessible workspaces",
+    description = "Return workspaces owned by, joined by, or publicly accessible to the current user.",
+    params(ListQuery),
+    responses(
+        (status = 200, description = "List of workspaces.", body = ApiResponse<Vec<Workspace>>),
+        (status = 401, description = "Unauthenticated.", body = ApiErrorResponse),
+        (status = 500, description = "Database read failed.", body = ApiErrorResponse)
+    )
+)]
+pub async fn handle(
+    service: web::Data<AppService>,
+    session: Session,
+    query: web::Query<ListQuery>,
+) -> Result<HttpResponse, AppError> {
+    let data = service
+        .workspace
+        .workspace_list(
+            &session,
+            query.limit.unwrap_or(50),
+            query.offset.unwrap_or(0),
+        )
+        .await?;
+    Ok(HttpResponse::Ok().json(ApiResponse::new(data)))
+}