refactor(data): move Result utility to utils and simplify API

Relocate the Result type from `@/data/result` to `@/utils/result` and
replace the discriminated-union API (`kind`/`value`) with a simpler
boolean-based API (`success`/`data`) across all repositories and
storage classes for improved readability and consistency.

src/data/storage/user/user_storage.ts

@@ -17,7 +17,7 @@
 
 import { UserSchema, type UserData } from "@/data/schemas/user/user";
 import { LocalStorage } from "../local_storage";
-import { type Result as ResultT } from "../result";
+import { type Result as ResultT } from "@/utils/result";
 import { StorageKeys } from "../storage_keys";
 import type { IUserStorage } from "./iuser_storage";
 
@@ -85,9 +85,9 @@ export class UserStorage implements IUserStorage {
 
   async clearUserData(): Promise<ResultT<void>> {
     const r1 = await this.clearUser();
-    if (r1.kind === "failure") return r1;
+    if (!r1.success) return r1;
     const r2 = await this.clearUserId();
-    if (r2.kind === "failure") return r2;
+    if (!r2.success) return r2;
     return this.clearAvatarUrl();
   }
 }