feat(identity): 收敛 AI Gateway 统一认证入口

Web 登录页合并为单一统一认证入口，未指定上下文时由认证中心在登录后决策。继续接受旧客户端显式传入 platform 或 tenant，并保持回调上下文及 tenant_hint 的绑定校验。同步更新 OpenAPI 产物。\n\n验证：Go 全量测试与 go vet 通过；Web lint、141 项 Vitest 和生产构建通过；本地 platform.admin 登录及管理工作台访问通过。

apps/web/src/components/AuthPanel.tsx

@@ -2,7 +2,6 @@ import type { FormEvent } from 'react';
 import { LogIn, UserPlus } from 'lucide-react';
 import { Button, Card, CardContent, CardHeader, CardTitle, Input, Label, PasswordInput, Tabs } from './ui';
 import type { AuthMode, LoadState, LoginForm, RegisterForm } from '../types';
-import type { OIDCContextType } from '../lib/oidc';
 
 const tabs = [
   { value: 'login', label: '账号登录' },
@@ -24,8 +23,7 @@ export function AuthPanel(props: {
   onSubmitLogin: (event: FormEvent<HTMLFormElement>) => void;
   onSubmitRegister: (event: FormEvent<HTMLFormElement>) => void;
   oidcEnabled: boolean;
-  oidcContextTypes: readonly OIDCContextType[];
-  onOIDCLogin: (contextType: OIDCContextType) => void;
+  onOIDCLogin: () => void;
 }) {
   return (
     <section className="authShell" aria-label="登录">
@@ -39,26 +37,14 @@ export function AuthPanel(props: {
         <CardContent className="authContent">
           {props.oidcEnabled ? (
             <div className="formGrid">
-              {props.oidcContextTypes.includes('platform') && (
-                <Button
-                  type="button"
-                  disabled={props.state === 'loading'}
-                  onClick={() => props.onOIDCLogin('platform')}
-                >
-                  <LogIn size={15} />
-                  使用平台账号登录
-                </Button>
-              )}
-              {props.oidcContextTypes.includes('tenant') && (
-                <Button
-                  type="button"
-                  disabled={props.state === 'loading'}
-                  onClick={() => props.onOIDCLogin('tenant')}
-                >
-                  <LogIn size={15} />
-                  使用租户账号登录
-                </Button>
-              )}
+              <Button
+                type="button"
+                disabled={props.state === 'loading'}
+                onClick={props.onOIDCLogin}
+              >
+                <LogIn size={15} />
+                使用统一认证登录
+              </Button>
             </div>
           ) : (
             <>