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/create.go

@@ -13,7 +13,7 @@ import (
 	"github.com/spf13/cobra"
 )
 
-var cDue, cContent, cDummy string
+var cDue, cContent string
 var cTags, cRels []string
 
 var createCmd = &cobra.Command{
@@ -60,11 +60,9 @@ var createCmd = &cobra.Command{
 
 func init() {
 	rootCmd.AddCommand(createCmd)
+	addPropertyFlags(createCmd)
+	createCmd.Flags().Set("type", "issue")
 	f := createCmd.Flags()
-	f.StringVar(&cDummy, "type", "issue", "")
-	f.StringVar(&cDummy, "status", "", "")
-	f.StringVar(&cDummy, "prio", "", "")
-	f.StringVar(&cDummy, "namespace", "", "")
 	f.StringVar(&cDue, "due", "", "")
 	f.StringVar(&cContent, "content", "", "")
 	f.StringArrayVar(&cTags, "tag", nil, "")