Refactor character affiliations to singular form

- Updated character data structure to replace 'affiliations' and 'frAffiliations' with 'affiliation' and 'frAffiliation'.
- Modified related functions and components to accommodate the new structure.
- Adjusted database schema and server-side logic to reflect the changes in character affiliation handling.
- Ensured all references in the UI components and data import/export scripts are updated accordingly.

src/lib/server/daily-character.ts

@@ -11,8 +11,8 @@ const characterWithRelationsSelect = {
 	frName: character.frName,
 	gender: character.gender,
 	age: character.age,
-	affiliations: character.affiliations,
-	frAffiliations: character.frAffiliations,
+	affiliation: character.affiliation,
+	frAffiliation: character.frAffiliation,
 	devilFruitId: character.devilFruitId,
 	devilFruitName: devilFruit.name,
 	devilFruitType: devilFruit.type,