Per-day send times and saved schedule presets

A campaign's send window (in the Settings tab, Send Window section) can use a different time range for each weekday. Turn on "Different time per day" and set a start and end for each selected send day — for example Monday to Thursday 09:00 to 17:00 but Friday only 09:00 to 12:00. Days you leave untouched use the campaign's main start and end time. When it is off, one window applies to every day, exactly as before, so existing campaigns are unchanged until you opt in. You can also save the whole schedule — days, hours, timezone, and any per-day times — as a named preset with "Save current" in the same Send Window section, then re-apply it to any campaign later from either the Settings tab or the launch dialog. Presets are shared across the workspace. Emails due outside a day's window are never dropped; they are held and sent at the next allowed time.