* feat(cron): configurable default timezone for cron expressions
Cron expressions (e.g. "0 8 * * *") are evaluated relative to a timezone.
Without an explicit per-job timezone, they default to the server's system
timezone, which may not match the user's local time — especially in Docker
containers (default UTC) or multi-region deployments.
This adds a `default_timezone` setting to `CronConfig` (IANA format, e.g.
"Asia/Ho_Chi_Minh") that is applied as fallback when a cron job has no
explicit `schedule.tz`. The setting is configurable via the UI config page
(Integrations → Cron Scheduler) and hot-reloads on config changes.
Backend:
- Add `DefaultTimezone` field to `CronConfig`
- Add `SetDefaultTimezone()` to `CronStore` interface + PG implementation
- Apply default TZ in `AddJob()` when `schedule.TZ` is empty
- Wire at startup + subscribe to config change events for hot reload
- Update cron tool description so LLM knows about gateway default
Frontend:
- Add timezone dropdown (20 common IANA timezones) to Cron config section
- Add i18n keys for en, vi, zh
* fix(cron): apply default timezone to existing jobs via computeNextRun
Pass defaultTZ as fallback to computeNextRun so existing cron jobs
(with timezone = NULL in DB) also use the gateway's configured default
timezone when computing next_run_at. This ensures old jobs benefit
from the timezone setting without needing a DB migration or backfill.
---------
Co-authored-by: Luvu182 <208665161+Luvu182@users.noreply.github.com>
- Update go.mod and Dockerfile to Go 1.26
- Apply `go fix ./...` stdlib modernizations across 170+ files
- Add `go fix` to post-implementation checklist in CLAUDE.md
- Fix go fix misapplied rewrite in loop_history.go
