DLManager: fix ETA dropping whole hours from time left display

[Burningflames86]

Problem

The "Time left:" display during downloads under-reports the remaining time
by whole hours, and periodically jumps backwards.

estimate was reused when splitting the ETA into its parts:

hours, estimate = int(estimate // 3600), estimate % 3600

Python evaluates the whole right-hand side first, then binds left to right,
so estimate was overwritten with the sub-hour remainder. The value later
passed to the UI as estimated_time_left was therefore always
estimate % 3600 — the whole-hours component was silently discarded.

Effect

true remaining	displayed
2:45:00	0:45:00
1:30:00	0:30:00
1:02:05	0:02:05
0:59:55	0:59:55

• Always renders as 0:MM:SS, under-reporting by whole hours
• Jumps back up to 0:00:0x each time the estimate crosses an hour
  boundary, so a multi-hour download looks like several sub-hour countdowns
• Only correct during the final hour of a download

The ETA log line was unaffected, because it formats from the separate
hours/minutes/seconds variables. That disagreement between the logged
ETA: and the on-screen label is the easiest way to observe this.

Fix

Keep the total in its own variable and pass that through to UIUpdate.
The logged ETA is unchanged.

Scope

rare/lgndr/downloader/mp/manager.py only (+6/-5). No changes to the ETA
log format, to get_time, or to any UI code — the existing formatting is
left as-is.

Verification

• The value sent to the UI now reconstructs the logged HH:MM:SS exactly:
  eta_total == hours * 3600 + minutes * 60 + seconds
• Confirmed against a live download — the label matches the logged ETA:
  and counts down monotonically across hour boundaries
• ruff clean; pylint reports no new issues

[loathingKernel]

Shouldn't this PR be made to https://github.com/legendary-gl/legendary too?

[Burningflames86]

Shouldn't this PR be made to https://github.com/legendary-gl/legendary too?
Legendary repository does not use the estimate variable once the hours, minutes and seconds are calculated from it. Meanwhile in the Rare repository it is dependent on this variable still for UI. (estimated_time_left=round(estimate) on line 164)

[loathingKernel]

Thank you for figuring this one out.