Refactor User entity and SignupRequest DTO to resolve method access issues and improve compatibility

- Added explicit getter/setter methods in User entity for use with service layer
- Implemented standard getters/setters in SignupRequest DTO
- Replaced incorrect imports from models.User to entity.User across services and repository

src/main/java/com/skycrate/backend/skycrateBackend/entity/User.java

@@ -87,4 +87,32 @@ public class User implements UserDetails {
     public String getFullname() {
         return fullname;
     }
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
 }