Add cron expression support for recurring reminders using robfig/cron/v3.
Changes:
- Migration #2: ALTER TABLE reminders ADD COLUMN cron TEXT + next_fire_ts INTEGER
- Reminder struct: add Cron and NextFireTs fields
- scanReminder helper extracts full row including nullable cron
- CreateReminder: accept optional cron param, store next_fire_ts = fire_ts
- DueReminders: query on next_fire_ts instead of fire_ts
- RescheduleReminder: new method — parse cron, compute next fire, update
next_fire_ts or mark fired if no more valid times
- Dispatcher: call RescheduleReminder for cron reminders, MarkReminder for
one-shots (preserving existing behavior for ID=0 digest skip)
- ReminderCompleter interface: add RescheduleReminder method
- storeAPI adapter: forward RescheduleReminder
- All callers updated: CreateReminder signature includes cron param
- Tests: TestRecurringReminder (store), TestDispatchRecurringReminderReschedules
- Existing tests updated for new signature
worker/server.go: dispatch now receives a per-connection context instead of
context.Background(), so handler cancellation propagates on conn close.
voice/server.go: same — per-conn context fed through safeDispatch into
HandlePushToTalk instead of context.Background().
store/reminders.go: propagate LastInsertId error.
store/nudges.go: propagate LastInsertId and RowsAffected errors.
store/tools.go: propagate RowsAffected error.
config/config.go: applyDefaults now respects StateDir when set, using it as
the base for empty DBPath/SocketPath instead of silently ignoring it.
phraser/llmphraser.go: close stderr pipe fd when cmd.Start() fails.
kami