refactor(admin): 管理后台 UI - 独立设计系统并与用户端隔离

把后台 token、Ant 主题、壳层控件和抽屉弹窗从用户工作台拆开，去掉树状侧栏装饰线，色板仍用原来的中性黑白台阶。

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/pages/admin/ui/overlays.tsx

@@ -0,0 +1,48 @@
+import { Drawer, Modal, type DrawerProps, type ModalProps } from "antd";
+import type { CSSProperties } from "react";
+
+import { cn } from "@/lib/utils";
+
+export type AdminDrawerProps = DrawerProps & {
+    flush?: boolean;
+};
+
+export type AdminModalProps = ModalProps & {
+    flush?: boolean;
+};
+
+const MODAL_FLUSH_STYLES = {
+    container: { padding: 0, overflow: "hidden" as const },
+    body: { padding: 0 },
+};
+
+function mergeFlushStyles(resolved: unknown, flush: boolean, kind: "drawer" | "modal") {
+    const base = resolved && typeof resolved === "object" ? (resolved as Record<string, unknown>) : {};
+    if (!flush) return base;
+    const body = base.body && typeof base.body === "object" ? (base.body as CSSProperties) : {};
+    if (kind === "drawer") return { ...base, body: { ...body, padding: 0 } };
+    const container = base.container && typeof base.container === "object" ? (base.container as CSSProperties) : {};
+    return {
+        ...base,
+        container: { ...container, ...MODAL_FLUSH_STYLES.container },
+        body: { ...body, ...MODAL_FLUSH_STYLES.body },
+    };
+}
+
+export function AdminDrawer({ flush = false, destroyOnHidden = true, styles, className, rootClassName, ...props }: AdminDrawerProps) {
+    const mergedStyles =
+        typeof styles === "function"
+            ? (info: { props: DrawerProps }) => mergeFlushStyles(styles(info), flush, "drawer")
+            : mergeFlushStyles(styles, flush, "drawer");
+
+    return <Drawer destroyOnHidden={destroyOnHidden} className={cn("admin-drawer-panel", className)} rootClassName={cn("admin-drawer", rootClassName)} {...props} styles={mergedStyles as DrawerProps["styles"]} />;
+}
+
+export function AdminModal({ flush = false, destroyOnHidden = true, styles, className, rootClassName, ...props }: AdminModalProps) {
+    const mergedStyles =
+        typeof styles === "function"
+            ? (info: { props: ModalProps }) => mergeFlushStyles(styles(info), flush, "modal")
+            : mergeFlushStyles(styles, flush, "modal");
+
+    return <Modal destroyOnHidden={destroyOnHidden} className={cn("admin-modal-panel", className)} rootClassName={cn("admin-modal-root", rootClassName)} {...props} styles={mergedStyles as ModalProps["styles"]} />;
+}