Traggo can't count

[jinks]

Describe the bug
When correcting a timespan that was originally created via tracker you have no ability to change the seconds that have been counted, but they sill factor into the time calculation.

Expected behavior
The time in the screenshot below should clearly be 1h 45m, not 44m. I have no way of changing this off-by-one-minute behavior.
Changing either time changes the amount of time, but it's always off, since the seconds in start and end don't ever change.

Screenshots

Suggested change
When changing the time interval via the date selector it should set seconds to "00" since you have no way of entering a value.

Additional
In my use case I need to track time in 15 minute intervals, so every timespan should be a multiple of 0.25 hours. It would be nice if one could pre-configure such fixed intervals.

[jmattheis]

I'm open to accept PRs for this.