more fixes

server/src/table_definition/handlers/post_table_definition.rs

@@ -203,8 +203,17 @@ async fn execute_table_definition(
         .map_err(|e| Status::internal(format!("Schema creation failed: {}", e)))?;
 
     let mut links = Vec::new();
+    let mut seen_tables = std::collections::HashSet::new();
+
     for link in request.links.drain(..) {
-        // CHANGED: Use schema_id instead of profile_id
+        // Check for duplicate link
+        if !seen_tables.insert(link.linked_table_name.clone()) {
+            return Err(Status::invalid_argument(format!(
+                "Duplicate link to table '{}'", 
+                link.linked_table_name
+            )));
+        }
+
         let linked_table = sqlx::query!(
             "SELECT id FROM table_definitions
              WHERE schema_id = $1 AND table_name = $2",