feat(proxy-checker): add serialization helpers to ProxyChekerResult

- import dataclasses.asdict and json
- add ProxyChekerResult.to_dict() to produce a plain dict
- add ProxyChekerResult.to_json() to produce a JSON string
- add ProxyChekerResult.__str__() to return JSON for easy printing

Improves result serialization and logging for proxy check results.

Author: dimaslanjaka

proxy_checker/ProxyChekerResult.py

@@ -1,5 +1,7 @@
 from dataclasses import dataclass
 from typing import List, Optional
+from dataclasses import asdict
+import json
 
 
 @dataclass
@@ -11,3 +13,15 @@ class ProxyChekerResult:
     country_code: Optional[str] = None
     proxy: Optional[str] = None
     error: bool = False
+
+    def to_dict(self) -> dict:
+        """Return a plain dict representation of the result."""
+        return asdict(self)
+
+    def to_json(self) -> str:
+        """Return a JSON string representation of the result."""
+        return json.dumps(self.to_dict())
+
+    def __str__(self) -> str:
+        """Human-readable JSON string for printing."""
+        return self.to_json()