Feat: Support multipart/mixed (#7155)

* feat(): support multipart mixed

fix: support vars interpolation on mixed multi-part

Update packages/bruno-electron/src/ipc/network/interpolate-vars.js

Co-authored-by: Timon <39559178+Its-treason@users.noreply.github.com>

refactor: use startsWith

feat: best effort for other multipart/* contentypes

* feat: enhance variable interpolation for multipart requests

- Updated `interpolateVars` function to support interpolation in multipart/form-data and multipart/mixed requests.
- Added handling for empty multipart arrays and parts with missing or undefined values.
- Improved type checks for content types to ensure proper interpolation behavior.

Includes new tests to validate the interpolation functionality for multipart requests.

* fix: normalize error handling in sendRequest and improve test reliability

---------

Co-authored-by: Alfonso Presa <alfonso-presa@users.noreply.github.com>

packages/bruno-js/src/sandbox/quickjs/shims/bru.js

@@ -471,20 +471,26 @@ const addBruShimToContext = (vm, bru) => {
   bruObject.dispose();
 
   vm.evalCode(`
+    // sendRequest with callback: normalize error.status (axios uses error.response.status) so
+    // tests like expect(error.status).to.eql(404) pass in safe sandbox; return response after
+    // success callback for consistent promise resolution.
     globalThis.bru.sendRequest = async (requestConfig, callback) => {
       if (!callback) return await globalThis.bru._sendRequest(requestConfig);
       try {
         const response = await globalThis.bru._sendRequest(requestConfig);
         try {
           await callback(null, response);
+          return response;
         }
         catch(error) {
           return Promise.reject(error);
         }
       }
       catch(error) {
+        const errObj = JSON.parse(JSON.stringify(error));
+        if (errObj && errObj.response && typeof errObj.response.status === 'number') errObj.status = errObj.response.status;
         try {
-          await callback(JSON.parse(JSON.stringify(error)), null);
+          await callback(errObj, null);
         }
         catch(err) {
           return Promise.reject(err);