refactor: simplify db and cmd flags, reduce code duplication

- Abstract property flags into addPropertyFlags in cmd/root.go and apply to commands
- Remove unused GetUserByUsername from db.go (it's redundant with service.resolveUserIDByName)
- Use configured user in WithMentions directly in inbox command
- Refactor resolve methods in node_service_sqlite.go to reduce duplication

cmd/inbox.go

@@ -18,17 +18,8 @@ var inboxCmd = &cobra.Command{
 			fmt.Fprintln(os.Stderr, err)
 			return
 		}
-		userID, err := d.GetUserByUsername(cfg.GetUser())
-		if err != nil {
-			fmt.Fprintln(os.Stderr, err)
-			return
-		}
-		if userID == "" {
-			output.PrintNodes(cmd.OutOrStdout(), nil, jsonFlag)
-			return
-		}
 		svc := service.NewSQLiteNodeService(d.DB, cfg.GetUser())
-		if nodes, err := svc.List(service.WithMentions(userID)); err == nil {
+		if nodes, err := svc.List(service.WithMentions(cfg.GetUser())); err == nil {
 			output.PrintNodes(cmd.OutOrStdout(), nodes, jsonFlag)
 		}
 	},