feat: assertion monitor enhancements

[dewanshparashar]

• Improved error handling: Replaced throwing errors with alert generation when no assertion logs are found in the search window, allowing monitoring to continue for all chains.

• Enhanced alert messages: Added detailed alerts that include:

  • Block range searched (from/to blocks)
  • Duration of search window (~X hours/days)
  • Chain activity status (active vs inactive)

• Chain activity detection: Added logic to detect if the chain is producing blocks during the search window, distinguishing between:

  • Active chain without assertions → Problem (validator not posting assertions)
  • Inactive chain without assertions → Expected (no blocks = no assertions needed)

• Fixed summary formatting: Fixed alert summary to properly separate chains with newlines instead of comma concatenation.