refactor: favicon 移回 app/ + 删除用户改为 RESTful DELETE /api/users/[id]

- favicon: 从 public/favicon.ico 移回 app/favicon.ico（next-on-pages 1.13.16 下生产验证 /favicon.ico 正常返回）
- 删除用户: POST /api/roles/delete 改为 DELETE /api/users/[id]，符合 RESTful 语义（资源 users + 标准 DELETE 方法）

app/api/roles/delete/route.ts

@@ -1,49 +0,0 @@
-import { createDb } from "@/lib/db";
-import { users, userRoles, apiKeys } from "@/lib/schema";
-import { eq } from "drizzle-orm";
-import { ROLES, PERMISSIONS } from "@/lib/permissions";
-import { checkPermission } from "@/lib/auth";
-import { getUserId } from "@/lib/apiKey";
-
-export const runtime = "edge";
-
-export async function POST(request: Request) {
-  const canManage = await checkPermission(PERMISSIONS.PROMOTE_USER);
-  if (!canManage) {
-    return Response.json({ error: "权限不足" }, { status: 403 });
-  }
-
-  try {
-    const { userId } = await request.json() as { userId: string };
-    if (!userId) {
-      return Response.json({ error: "缺少必要参数" }, { status: 400 });
-    }
-
-    const currentUserId = await getUserId();
-    if (userId === currentUserId) {
-      return Response.json({ error: "不能删除自己" }, { status: 400 });
-    }
-
-    const db = createDb();
-
-    const currentUserRole = await db.query.userRoles.findFirst({
-      where: eq(userRoles.userId, userId),
-      with: {
-        role: true,
-      },
-    });
-
-    if (currentUserRole?.role.name === ROLES.EMPEROR) {
-      return Response.json({ error: "不能删除皇帝" }, { status: 400 });
-    }
-
-    // apiKeys 未配置级联删除，需先手动删除；其余（accounts / emails→messages / webhooks / userRoles）由外键级联处理
-    await db.delete(apiKeys).where(eq(apiKeys.userId, userId));
-    await db.delete(users).where(eq(users.id, userId));
-
-    return Response.json({ success: true });
-  } catch (error) {
-    console.error("Failed to delete user:", error);
-    return Response.json({ error: "操作失败" }, { status: 500 });
-  }
-}