feat: 品牌裁剪弹窗/Markdown 行内短代码与详情视频块等

新增：
- BrandCropModal 品牌图裁剪弹窗 + cropImage 工具
- Markdown 行内短代码（inlineShortcodes + remark 插件）
- MdDetails 折叠块、MdVideo 视频块组件
- directiveBlocks/inlineShortcodes 测试

其它：
- 聊天后端（handler/service chat）调整
- Markdown 渲染链路、编辑器、全局样式与品牌相关面板更新

frontend/app/admin/settings/BrandMediaPicker.tsx

@@ -3,8 +3,8 @@
 import { Images, Loader2 } from "lucide-react";
 import { useEffect, useState } from "react";
 import Modal from "@/components/Modal";
-import { apiMyMedia, type MediaAttachment } from "@/lib/api";
-import { mediaURLFitsSlot, type BrandSlot } from "@/lib/brand";
+import { apiAdminMediaLibrary, apiMyMedia } from "@/lib/api";
+import { normalizeBrandURL, type BrandSlot } from "@/lib/brand";
 import { isOwnImage, variantURL, widthSrcSet } from "@/lib/responsiveImage";
 
 const SLOT_LABEL: Record<BrandSlot, string> = {
@@ -13,6 +13,13 @@ const SLOT_LABEL: Record<BrandSlot, string> = {
   favicon: "Favicon",
 };
 
+/** 选图条目：本人附件带 attachmentId；品牌目录历史图仅 URL（已在品牌目录，无需复制） */
+export type BrandPickItem = {
+  key: string;
+  url: string;
+  attachmentId: number | null;
+};
+
 export default function BrandMediaPicker({
   open,
   slot,
@@ -22,9 +29,9 @@ export default function BrandMediaPicker({
   open: boolean;
   slot: BrandSlot;
   onClose: () => void;
-  onPick: (item: MediaAttachment) => void;
+  onPick: (item: BrandPickItem) => void;
 }) {
-  const [items, setItems] = useState<MediaAttachment[]>([]);
+  const [items, setItems] = useState<BrandPickItem[]>([]);
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState("");
 
@@ -33,16 +40,29 @@ export default function BrandMediaPicker({
     let cancelled = false;
     setLoading(true);
     setError("");
-    void apiMyMedia()
-      .then((res) => {
+    // 本人附件 + 媒体库盘点里的品牌目录历史图（品牌图不落附件，需合并展示）
+    Promise.all([apiMyMedia(), apiAdminMediaLibrary().catch(() => null)])
+      .then(([mediaRes, libRes]) => {
         if (cancelled) return;
-        if (res.error) {
-          setError(res.error);
+        if (mediaRes.error) {
+          setError(mediaRes.error);
           setItems([]);
           return;
         }
-        const all = res.attachments || [];
-        setItems(all.filter((item) => mediaURLFitsSlot(slot, item.url)));
+        const out: BrandPickItem[] = (mediaRes.attachments || []).map((a) => ({
+          key: `att-${a.id}`,
+          url: a.url,
+          attachmentId: a.id,
+        }));
+        const seen = new Set(out.map((i) => i.url));
+        for (const it of libRes?.items || []) {
+          if (it.category !== "brand") continue;
+          if (!normalizeBrandURL(slot, it.url)) continue;
+          if (seen.has(it.url)) continue;
+          seen.add(it.url);
+          out.unshift({ key: `brand-${it.url}`, url: it.url, attachmentId: null });
+        }
+        setItems(out);
       })
       .catch(() => {
         if (!cancelled) setError("加载媒体库失败");
@@ -59,7 +79,7 @@ export default function BrandMediaPicker({
     <Modal
       open={open}
       title={`从媒体库选择 · ${SLOT_LABEL[slot]}`}
-      description="只列出格式符合的图片。保存后会复制一份到品牌目录，之后删除原图不会影响 Logo。"
+      description="位图选中后进入裁剪并转成 WebP；SVG / ICO 与历史品牌图直接引用，之后删除原图不会影响 Logo。"
       onClose={onClose}
       maxWidthClass="max-w-lg"
       dismissOnOverlay
@@ -73,12 +93,12 @@ export default function BrandMediaPicker({
           {error}
         </p>
       ) : items.length === 0 ? (
-        <p className="meta text-[13px] py-6 text-center">没有可用图片。Logo 需要 PNG / WebP / SVG，Favicon 还可选 ICO。</p>
+        <p className="meta text-[13px] py-6 text-center">媒体库还没有图片，先上传一张吧。</p>
       ) : (
         <div className="grid grid-cols-4 sm:grid-cols-5 gap-2">
           {items.map((item) => (
             <button
-              key={item.id}
+              key={item.key}
               type="button"
               onClick={() => {
                 onPick(item);