refactor(shared): FilePath VO uses __post_init__ instead of custom __init__

Custom __init__ on a @dataclass(frozen=True) is a code smell — it
bypasses the generated dataclass __init__ and re-implements the
str/Path coercion + frozen-aware setattr by hand. Replaced with a
single __post_init__ that performs the same normalization. Same
public API (FilePath(str) and FilePath(Path) both work), same
behavior, no callers touched.

alfred/domain/shared/value_objects.py

@@ -43,29 +43,21 @@ class ImdbId:
 @dataclass(frozen=True)
 class FilePath:
     """
-    Value object representing a file path with validation.
+    Value object representing a file path.
 
-    Ensures the path is valid and optionally checks existence.
+    Accepts either ``str`` or :class:`pathlib.Path` at construction;
+    the value is normalized to ``Path`` in ``__post_init__``.
     """
 
     value: Path
 
-    def __init__(self, path: str | Path):
-        """
-        Initialize FilePath.
-
-        Args:
-            path: String or Path object representing the file path
-        """
-        if isinstance(path, str):
-            path_obj = Path(path)
-        elif isinstance(path, Path):
-            path_obj = path
-        else:
-            raise ValidationError(f"Path must be str or Path, got {type(path)}")
-
-        # Use object.__setattr__ because dataclass is frozen
-        object.__setattr__(self, "value", path_obj)
+    def __post_init__(self) -> None:
+        if isinstance(self.value, Path):
+            return
+        if isinstance(self.value, str):
+            object.__setattr__(self, "value", Path(self.value))
+            return
+        raise ValidationError(f"Path must be str or Path, got {type(self.value)}")
 
     def __str__(self) -> str:
         return str(self.value)