semantic markup update

frontend/src/routes/migration/mappings/+page.svelte

@@ -32,6 +32,8 @@
 
   // [DEF:fetchEnvironments:Function]
   // @PURPOSE: Fetches the list of environments.
+  // @PRE: None.
+  // @POST: environments array is populated.
   async function fetchEnvironments() {
     try {
       const response = await fetch('/api/environments');
@@ -50,6 +52,8 @@
   // [DEF:fetchDatabases:Function]
   /**
    * @purpose Fetches databases from both environments and gets suggestions.
+   * @pre sourceEnvId and targetEnvId must be set.
+   * @post sourceDatabases, targetDatabases, mappings, and suggestions are updated.
    */
   async function fetchDatabases() {
     if (!sourceEnvId || !targetEnvId) return;
@@ -86,6 +90,8 @@
   // [DEF:handleUpdate:Function]
   /**
    * @purpose Saves a mapping to the backend.
+   * @pre event.detail contains sourceUuid and targetUuid.
+   * @post Mapping is saved and local mappings list is updated.
    */
   async function handleUpdate(event: CustomEvent) {
     const { sourceUuid, targetUuid } = event.detail;