[FEATURE]: Format long retry backoff durations into human-readable time strings

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Feature Description

In the Web UI, when a request fails and enters a long retry backoff state, the countdown status is currently rendered as raw total seconds (e.g., Retrying in 40269 seconds - Attempt 1).

Proposed Solution

Format large second values into human-readable duration strings (e.g., 11h 11m 09s, 2m 15s) for retry countdown displays.

Benefits

• Dramatically improves UI readability for large backoff delays.
• Eliminates the need for users to manually calculate hours/minutes from large second counts.