Improve error handling in Jira Cloud auth validation (#2114)

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Fixes OPS-3427


<img width="972" height="780" alt="image"
src="https://github.com/user-attachments/assets/7b770f1e-751a-4b36-88d2-a3307e6caca1"
/>

Author: Roman Snapko

packages/blocks/jira-cloud/src/auth.ts

@@ -44,7 +44,7 @@ You can generate your API token from:
     } catch (e) {
       return {
         valid: false,
-        error: ((e as HttpError).response.body as any).message,
+        error: (e as HttpError)?.message ?? 'Invalid credentials',
       };
     }
   },