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/routes.rs

@@ -2,7 +2,12 @@ use actix_web::web;
 use actix_web::web::scope;
 
 use crate::api::auth;
+use crate::api::workspace;
 
 pub fn init_routes(cfg: &mut web::ServiceConfig) {
-    cfg.service(scope("/api/v1").configure(auth::configure));
+    cfg.service(
+        scope("/api/v1")
+            .configure(auth::configure)
+            .configure(workspace::configure),
+    );
 }