Add retrieval method for all file types in files service

Implemented the `getAllFilesTypes` method to retrieve all file types from the database. This method uses the database connection to select and return an array of file types, completing the previously marked TODO item.

apps/backend/src/app/files/files.service.ts

@@ -280,8 +280,17 @@ export class FilesService {
 		}
 	}
 
+	/**
+	 * Retrieves all file types from the database.
+	 *
+	 * @return {Promise<Array>} Promise that resolves to an array of file types.
+	 */
 	public async getAllFilesTypes() {
-		//TODO
+		return await this.database.use()
+			.select()
+			.from(FilesTypesTable)
+			.prepare("getAllFilesTypes")
+			.execute()
 	}
 
 	public async removeFileType() {