Add ticket time tracking with reports and entry management.

Support start/stop timer, manual durations, grouped reports, and per-ticket edit/delete of time entries with undo.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/ticket/timestore.go

@@ -0,0 +1,16 @@
+package ticket
+
+import "time"
+
+// TimeStore persists time entries and the optional active timer.
+type TimeStore interface {
+	List() ([]TimeEntry, error)
+	ListByTicket(ticketID string) ([]TimeEntry, error)
+	Create(e TimeEntry) (TimeEntry, error)
+	Update(e TimeEntry) error
+	Delete(id string) error
+	SumByTicket(ticketID string) (time.Duration, error)
+
+	LoadActiveTimer() (*ActiveTimer, error)
+	SaveActiveTimer(t *ActiveTimer) error // nil clears
+}