feat: 添加 Admin 管理后台

- 数据库新增 Role 枚举、disabled 字段和 McpCallLog 调用日志表
- 后端新增 requireAdmin 中间件和 /api/admin/* 管理接口（统计、用户、项目、日志）
- MCP 工具调用自动记录详细日志（耗时、参数、响应大小、客户端IP、token估算）
- 前端新增 /admin 路由区域：仪表盘、用户管理、项目管理、调用日志四个页面
- JWT 携带 role 字段，登录/OAuth 增加禁用账号检查
- nginx 配置补充 X-Forwarded-For 透传真实客户端 IP

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

prisma/migrations/20260404120000_add_admin_role_and_call_logs/migration.sql

@@ -0,0 +1,34 @@
+-- CreateEnum
+CREATE TYPE "Role" AS ENUM ('USER', 'ADMIN');
+
+-- AlterTable
+ALTER TABLE "User" ADD COLUMN "role" "Role" NOT NULL DEFAULT 'USER';
+ALTER TABLE "User" ADD COLUMN "disabled" BOOLEAN NOT NULL DEFAULT false;
+
+-- CreateTable
+CREATE TABLE "McpCallLog" (
+    "id" TEXT NOT NULL,
+    "projectId" TEXT NOT NULL,
+    "toolName" TEXT NOT NULL,
+    "calledAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "durationMs" INTEGER NOT NULL,
+    "success" BOOLEAN NOT NULL,
+    "requestParams" JSONB NOT NULL DEFAULT '{}',
+    "responseSize" INTEGER NOT NULL DEFAULT 0,
+    "clientIp" TEXT NOT NULL DEFAULT '',
+    "estimatedTokens" INTEGER,
+
+    CONSTRAINT "McpCallLog_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "McpCallLog_projectId_idx" ON "McpCallLog"("projectId");
+
+-- CreateIndex
+CREATE INDEX "McpCallLog_calledAt_idx" ON "McpCallLog"("calledAt");
+
+-- CreateIndex
+CREATE INDEX "McpCallLog_toolName_idx" ON "McpCallLog"("toolName");
+
+-- AddForeignKey
+ALTER TABLE "McpCallLog" ADD CONSTRAINT "McpCallLog_projectId_fkey" FOREIGN KEY ("projectId") REFERENCES "Project"("id") ON DELETE CASCADE ON UPDATE CASCADE;