refactor(models): unify table names to singular form for consistency across models

app/models/playlist.py

@@ -17,14 +17,14 @@ if TYPE_CHECKING:
 class Playlist(db.Model):
     """Model for playlists containing sounds."""
 
-    __tablename__ = "playlists"
+    __tablename__ = "playlist"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     name: Mapped[str] = mapped_column(String(255), nullable=False)
     description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
     genre: Mapped[Optional[str]] = mapped_column(String(100), nullable=True)
     user_id: Mapped[Optional[int]] = mapped_column(
-        Integer, ForeignKey("users.id"), nullable=True
+        Integer, ForeignKey("user.id"), nullable=True
     )
     is_main: Mapped[bool] = mapped_column(
         Boolean, default=False, nullable=False