Remove bbolt database dependency

Replaced bbolt-based database handling with Fyne built-in preferences for storing application settings. Deleted migration logic, database initialization, and error handling related to bbolt, simplifying the codebase and reducing external dependencies.

setting/entity.go

@@ -1,6 +1,6 @@
 package setting
 
 type Setting struct {
-	Code  string `json:"code"`
-	Value string `json:"value"`
+	Code  string
+	Value string
 }