Summary

• persist task-level timezone in scheduled_tasks, so recurring tasks keep their original timezone across runs
• update scheduler to compute cron next_run using task timezone first, with fallback to app default timezone
• add DB migration (schema version 12) to add scheduled_tasks.timezone for existing installations
• include timezone in scheduled task list output for easier troubleshooting
• add timezone: auto support: resolve machine timezone at runtime (fallback UTC)
• setup wizard defaults timezone to auto, adds common timezone picker options, and supports custom manual input

Validation

• cargo test
• npm --prefix web run build
• npm --prefix website run build

Closes #194