fix(@angular/build): handle relative URLs when constructing new URLs during server fetch

Ensures proper handling of relative URLs to prevent errors in server-side fetch operations.

Closes #29236

(cherry picked from commit a0b4ea2)

Author: alan-agius4

Diff for: packages/angular/build/src/utils/server-rendering/fetch-patch.ts

@@ -28,9 +28,9 @@ export function patchFetchToLoadInMemoryAssets(baseURL: URL): void {
     if (input instanceof URL) {
       url = input;
     } else if (typeof input === 'string') {
-      url = new URL(input);
+      url = new URL(input, baseURL);
     } else if (typeof input === 'object' && 'url' in input) {
-      url = new URL(input.url);
+      url = new URL(input.url, baseURL);
     } else {
       return originalFetch(input, init);
     }