Fix #745: warning realert window uses repeat_alert, not time_warning_fail_length

[bmfmancini]

Summary

Fixes #745.

The type 2 (time-based) warning re-alert window was computed from time_warning_fail_length (the warning time-window length) instead of repeat_alert (the configured re-alert interval). The $ra guard's truthy test used the same wrong field.

// Warning path (wrong — before):
$realerttime = ($thold_data['time_warning_fail_length'] - 1) * $step;
$ra = (... && $thold_data['time_warning_fail_length'] && ...);

// Alert path (correct — unchanged):
$realerttime = ($thold_data['repeat_alert'] - 1) * $step;
$ra = (... && $thold_data['repeat_alert'] && ...);

Impact

Warning re-alerts fired at a cadence controlled by the wrong setting (time_warning_fail_length) rather than the configured re-alert interval (repeat_alert).

Fix

Both the $realerttime computation and the $ra guard now use repeat_alert, matching the alert path at thold_functions.php:3136.

Testing

• php -l thold_functions.php — no syntax errors.
• Diff is two field-name changes only; indentation preserved.

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[somethingwithproof]

The repeat_alert correction is directionally correct, but this branch also carries three unrelated threshold_value edits from #789. Please remove those hunks so this PR contains only #745, then add Cacti-Composer/Pest coverage for initial warning, no early re-alert, and re-alert at the configured interval. A syntax check cannot validate this state machine, and the current integration matrix is red.