Task 1.1: Fix PEP 8 compliance in Serie class

- Fixed line length issues (max 79 chars)
- Added UTF-8 encoding to file operations
- Fixed blank line formatting
- Improved code formatting in __str__, to_dict, from_dict methods
- All docstrings now comply with PEP 8
- All 16 Serie class tests pass
- All 5 anime model tests pass
- No functional changes, only style improvements

src/core/entities/series.py

@@ -5,21 +5,33 @@ class Serie:
     """
     Represents an anime series with metadata and episode information.
     
-    The `key` property is the unique identifier for the series (provider-assigned, URL-safe).
-    The `folder` property is the filesystem folder name (metadata only, not used for lookups).
+    The `key` property is the unique identifier for the series
+    (provider-assigned, URL-safe).
+    The `folder` property is the filesystem folder name
+    (metadata only, not used for lookups).
     
     Args:
-        key: Unique series identifier from provider (e.g., "attack-on-titan"). Cannot be empty.
+        key: Unique series identifier from provider
+            (e.g., "attack-on-titan"). Cannot be empty.
         name: Display name of the series
         site: Provider site URL
-        folder: Filesystem folder name (metadata only, e.g., "Attack on Titan (2013)")
-        episodeDict: Dictionary mapping season numbers to lists of episode numbers
+        folder: Filesystem folder name (metadata only,
+            e.g., "Attack on Titan (2013)")
+        episodeDict: Dictionary mapping season numbers to
+            lists of episode numbers
         
     Raises:
         ValueError: If key is None or empty string
     """
     
-    def __init__(self, key: str, name: str, site: str, folder: str, episodeDict: dict[int, list[int]]):
+    def __init__(
+        self,
+        key: str,
+        name: str,
+        site: str,
+        folder: str,
+        episodeDict: dict[int, list[int]]
+    ):
         if not key or not key.strip():
             raise ValueError("Serie key cannot be None or empty")
         
@@ -31,15 +43,20 @@ class Serie:
         
     def __str__(self):
         """String representation of Serie object"""
-        return f"Serie(key='{self.key}', name='{self.name}', site='{self.site}', folder='{self.folder}', episodeDict={self.episodeDict})"
+        return (
+            f"Serie(key='{self.key}', name='{self.name}', "
+            f"site='{self.site}', folder='{self.folder}', "
+            f"episodeDict={self.episodeDict})"
+        )
 
     @property
     def key(self) -> str:
         """
         Unique series identifier (primary identifier for all lookups).
         
-        This is the provider-assigned, URL-safe identifier used throughout the application
-        for series identification, lookups, and operations.
+        This is the provider-assigned, URL-safe identifier used
+        throughout the application for series identification,
+        lookups, and operations.
         
         Returns:
             str: The unique series key
@@ -116,25 +133,34 @@ class Serie:
             "name": self.name,
             "site": self.site,
             "folder": self.folder,
-            "episodeDict": {str(k): list(v) for k, v in self.episodeDict.items()}
+            "episodeDict": {
+                str(k): list(v) for k, v in self.episodeDict.items()
+            }
         }
 
     @staticmethod
     def from_dict(data: dict):
         """Create a Serie object from dictionary."""
-        episode_dict = {int(k): v for k, v in data["episodeDict"].items()}  # Convert keys to int
-        return Serie(data["key"], data["name"], data["site"], data["folder"], episode_dict)
-
+        # Convert keys to int
+        episode_dict = {
+            int(k): v for k, v in data["episodeDict"].items()
+        }
+        return Serie(
+            data["key"],
+            data["name"],
+            data["site"],
+            data["folder"],
+            episode_dict
+        )
 
     def save_to_file(self, filename: str):
         """Save Serie object to JSON file."""
-        with open(filename, "w") as file:
+        with open(filename, "w", encoding="utf-8") as file:
             json.dump(self.to_dict(), file, indent=4)
 
-
     @classmethod
     def load_from_file(cls, filename: str) -> "Serie":
         """Load Serie object from JSON file."""
-        with open(filename, "r") as file:
+        with open(filename, "r", encoding="utf-8") as file:
             data = json.load(file)
         return cls.from_dict(data)