Replace generic "Unknown error" messages with descriptive error details (#18019)

## Summary

- Replace all generic `"Unknown error"` fallback messages across the
server codebase with messages that include the actual error details
- The most impactful change is in `guard-redirect.service.ts`, which
handles OAuth redirect errors — non-`AuthException` errors (e.g.,
passport state verification failures) now show `"Authentication error:
<actual message>"` instead of the opaque `"Unknown error"`
- Gmail/Google error handler services now include the error message in
the thrown exception instead of discarding it
- Other catch blocks (workflow delay resume, migration runner rollback,
code interpreter, marketplace) now use `String(error)` for non-Error
objects instead of a static fallback

Fixes the class of issues reported in
https://github.com/twentyhq/twenty/issues/17812, where a user saw
"Unknown error" during Google OAuth and had no way to diagnose the root
cause (which turned out to be a session cookie / SSL configuration
issue).

## Test plan

- [ ] Verify OAuth error flows (e.g., Google Auth with misconfigured
callback URL) now display the actual error message on the `/verify` page
instead of "Unknown error"
- [ ] Verify Gmail sync error handling still correctly classifies and
re-throws errors with descriptive messages
- [ ] Verify workflow delay resume failures include the error details in
the workflow run status


Made with [Cursor](https://cursor.com)

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/twenty-server/src/modules/workflow/workflow-executor/workflow-actions/delay/jobs/resume-delayed-workflow.job.ts

@@ -101,7 +101,7 @@ export class ResumeDelayedWorkflowJob {
           error:
             error instanceof Error
               ? error.message
-              : 'Unknown error during delay resume',
+              : `Error during delay resume: ${String(error)}`,
         });
       }
     }, authContext);