Add DST (Daylight Saving Time) support for Ava timezone

Currently Ava uses hardcoded EST (UTC-5) year-round. During Daylight Saving Time (roughly March-November), it should use EDT (UTC-4).

Current Code

Omni/Ava/Telegram/Bot.hs has:

let easternTZ = minutesToTimeZone (-300) -- Eastern Standard Time

Options

1. Use tz library - Add tz or timezone-olson package to read system timezone files 2. Simple date check - Check if current date falls within DST period (2nd Sunday March - 1st Sunday November) 3. Environment variable - Set TZ in systemd service and use getCurrentTimeZone

Files

• Omni/Ava/Telegram/Bot.hs - main timezone usage (lines 1072, 1498)
• Omni/Ava/Telegram/Heartbeat.hs - also uses timezone

Context

The systemd service doesn't inherit system timezone properly, which is why we hardcoded it.