refactor(db): thread context.Context through all Store methods

Enables request-scoped cancellation, timeouts, and graceful shutdown
for all database operations across API handlers, CLI commands, and TUI.

internal/tui/model.go

@@ -1,6 +1,7 @@
 package tui
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"time"
@@ -1095,7 +1096,7 @@ func (m model) reloadDetail(id string) tea.Cmd {
 	return tea.Batch(
 		loadEntities(m.store, m.listParams()),
 		func() tea.Msg {
-			e, err := m.store.Get(id)
+			e, err := m.store.Get(context.Background(), id)
 			if err != nil {
 				return errMsg{err}
 			}