[Improved, Fixed, Removed] Reliability and UI cleanup update

Improvements

• ATS stage updates are now more resilient, with automatic retries that reduce the chance of missed stage changes when JazzHR rate-limits or other transient errors occur.
• Stage mapping errors are handled gracefully, preventing stalled candidate progress indicators and reducing the need for manual support intervention.
• Capture-metrics reports load up to five times faster and no longer time-out on busy accounts, making analytics pages more reliable.

Fixes

• Corrected a rare error that could appear when an ATS integration had been deleted, ensuring webhooks no longer return a 500 message.
• Eliminated occasional 504 time-outs that occurred when generating company capture metrics.

Removed

• The “What happens next” onboarding card has been taken out of the dashboard to streamline the initial setup flow.