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

service/workspace/billing.rs

@@ -3,7 +3,7 @@ use uuid::Uuid;
 
 use crate::error::AppError;
 use crate::models::common::Role;
-use crate::models::workspaces::WorkspaceBilling;
+use crate::models::workspaces::{Workspace, WorkspaceBilling};
 use crate::service::WorkspaceService;
 use crate::session::Session;
 
@@ -20,27 +20,25 @@ impl WorkspaceService {
     pub async fn workspace_billing(
         &self,
         ctx: &Session,
-        workspace_id: Uuid,
+        ws: &Workspace,
     ) -> Result<WorkspaceBilling, AppError> {
         let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
-        let ws = self.find_workspace_by_id(workspace_id).await?;
         self.ensure_workspace_role_at_least(user_uid, &ws, Role::Owner)
             .await?;
-        self.ensure_workspace_billing(workspace_id).await
+        self.ensure_workspace_billing(ws.id).await
     }
 
     pub async fn workspace_update_billing(
         &self,
         ctx: &Session,
-        workspace_id: Uuid,
+        ws: &Workspace,
         params: UpdateBillingParams,
     ) -> Result<WorkspaceBilling, AppError> {
         let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
-        let ws = self.find_workspace_by_id(workspace_id).await?;
         self.ensure_workspace_role_at_least(user_uid, &ws, Role::Owner)
             .await?;
 
-        let current = self.ensure_workspace_billing(workspace_id).await?;
+        let current = self.ensure_workspace_billing(ws.id).await?;
         let plan = params.plan.unwrap_or(current.plan.clone());
         let billing_email = merge_optional_text(params.billing_email, current.billing_email);
         let seats = params.seats.unwrap_or(current.seats);
@@ -70,7 +68,7 @@ impl WorkspaceService {
         .bind(&billing_email)
         .bind(seats)
         .bind(now)
-        .bind(workspace_id)
+        .bind(ws.id)
         .fetch_one(&mut *txn)
         .await
         .map_err(AppError::Database)?;