Address code review findings across relay, UI, and Go backend

- relay: key uploadables map by actual variable name instead of iteration
  index so order-mismatch between Object.keys passes can't desync the
  multipart map from form field names
- mcp/v1: drop dead commented middleware line
- DurationPicker: tighten parse regex to require PT prefix for M/H and P
  for D/W, and reject NaN in stringify so cleared inputs don't produce
  invalid duration strings

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

packages/relay/src/fetch.ts

@@ -60,15 +60,16 @@ export const makeFetchQuery = (endpoint: string): FetchFunction => {
             const uploadableMap: {
                 [key: string]: string[];
             } = {};
+            const uploadableKeys = Object.keys(uploadables);
 
-            Object.keys(uploadables).forEach((key, index) => {
-                uploadableMap[index] = [`variables.${key}`];
+            uploadableKeys.forEach((key) => {
+                uploadableMap[key] = [`variables.${key}`];
             });
 
             formData.append("map", JSON.stringify(uploadableMap));
 
-            Object.keys(uploadables).forEach((key, index) => {
-                formData.append(index.toString(), uploadables[key]);
+            uploadableKeys.forEach((key) => {
+                formData.append(key, uploadables[key]);
             });
 
             requestInit.body = formData;