[FEATURE] add optional timezone field (IANA tz, e.g. America/Los_Angeles) to scheduled-trigger cron expressions

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

UTC cron drifts by 1 hour at each DST transition, forcing users to either (a) accept the drift, or (b) manually update their triggers twice a year. Prior art:

• systemd timers: OnCalendar= + TimeZone=
• Kubernetes CronJob: spec.timeZone (stable since v1.27)
• GitHub Actions schedule: cron docs note the UTC limitation as a known sharp edge
• AWS EventBridge Scheduler, GCP Cloud Scheduler, Heroku Scheduler all support tz

Impact

Right now every scheduled Claude Code trigger with a user-facing "run at X local time" semantic is subtly broken twice a year for many users. For low-frequency triggers (daily/weekly) this can be acceptable friction; for hourly or shift-aligned ones it's genuinely wrong.

Proposed Solution

A sibling field — {cron_expression, timezone} — rather than embedding TZ= inside the cron string (cleaner API surface)

Alternative Solutions

A default timezone could be honored, but I mean "America/Los_Angeles" not "Pacific Daylight Time". But it would still be nice to be able to override it.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

I want a report at 8am. Currently in daylight saving/summer time observing places, this will be off by a hour for several months of the year without a manual reschedule.

Sometimes these tasks MUST run at a certain time.