refactor: restructure core→server, split large entity files into database module

- Move src/core/ → src/server/
- Split SerieList.py (531 lines) and series.py (414 lines) into src/server/database/
- Add database/models.py for SQLAlchemy models
- Update all test imports to reflect new structure
- Remove deprecated test files (test_serie_class.py, test_serie_folder_with_year.py)

src/server/database/models.py

@@ -190,6 +190,54 @@ class AnimeSeries(Base, TimestampMixin):
             f"name='{self.name}')>"
         )
 
+    @property
+    def episodeDict(self) -> dict[int, list[int]]:
+        """Build episode dictionary from episodes relationship or private cache.
+
+        Returns:
+            Dictionary mapping season numbers to lists of episode numbers
+        """
+        # Check for private cache first (set when loading from JSON without DB)
+        if hasattr(self, '_episode_dict_cache') and self._episode_dict_cache is not None:
+            return self._episode_dict_cache
+        
+        episode_dict: dict[int, list[int]] = {}
+        if self.episodes:
+            for ep in self.episodes:
+                season = ep.season or 1
+                if season not in episode_dict:
+                    episode_dict[season] = []
+                episode_dict[season].append(ep.episode_number or 0)
+        return episode_dict
+
+    @property
+    def name_with_year(self) -> str:
+        """Get series name with year appended if available.
+
+        Returns:
+            Name in format "Name (Year)" if year is available, else just name
+        """
+        if self.year:
+            import re
+            year_suffix = f" ({self.year})"
+            clean_name = re.sub(r'(\s*\(\d{4}\))+\s*$', '', self.name or '').strip()
+            return f"{clean_name}{year_suffix}"
+        return self.name or ''
+
+    @property
+    def sanitized_folder(self) -> str:
+        """Get filesystem-safe folder name from display name with year.
+
+        Returns:
+            Sanitized folder name based on display name with year
+        """
+        from src.server.utils.filesystem import sanitize_folder_name
+        name_to_sanitize = self.name_with_year or self.folder or self.key
+        try:
+            return sanitize_folder_name(name_to_sanitize)
+        except ValueError:
+            return sanitize_folder_name(self.key)
+
 
 class Episode(Base, TimestampMixin):
     """SQLAlchemy model for anime episodes.