feat(guild-messaging): add seq-range pagination with limit for message listing

Fabric.Backend.Guild/src/messaging/messaging.controller.ts

@@ -16,6 +16,8 @@ type Message = {
 };
 
 const EDIT_WINDOW_MS = 15 * 60 * 1000;
+const DEFAULT_PAGE_LIMIT = 50;
+const MAX_PAGE_LIMIT = 200;
 
 @Controller('channels/:id/messages')
 export class MessagingController {
@@ -85,12 +87,28 @@ export class MessagingController {
     @Param('id') channelId: string,
     @Query('seq_from') seqFrom?: string,
     @Query('seq_to') seqTo?: string,
+    @Query('limit') limit?: string,
   ) {
     const from = seqFrom ? Number(seqFrom) : 1;
     const to = seqTo ? Number(seqTo) : Number.MAX_SAFE_INTEGER;
+    const requestedLimit = limit ? Number(limit) : DEFAULT_PAGE_LIMIT;
+    const safeLimit =
+      Number.isFinite(requestedLimit) && requestedLimit > 0
+        ? Math.min(requestedLimit, MAX_PAGE_LIMIT)
+        : DEFAULT_PAGE_LIMIT;
     const arr = this.messagesByChannel.get(channelId) ?? [];
+    const filtered = arr.filter((m) => m.seq >= from && m.seq <= to);
+    const items = filtered.slice(0, safeLimit);
+
     return {
-      items: arr.filter((m) => m.seq >= from && m.seq <= to),
+      items,
+      page: {
+        seqFrom: from,
+        seqTo: to,
+        limit: safeLimit,
+        returned: items.length,
+        hasMore: filtered.length > items.length,
+      },
     };
   }
 }

docs/TODO-backend-center-guild.md

@@ -47,7 +47,7 @@
 - [x] 发送消息（content/reply/mentions/attachments 元数据）
 - [x] 编辑消息（可编辑窗口策略先简化）
 - [x] 删除消息（软删 vs 硬删，先定策略）
-- [ ] `GET messages` 分页（seq 区间 + limit）
+- [x] `GET messages` 分页（seq 区间 + limit）
 - [ ] seq 分配改为 DB 原子方案（避免并发冲突）
 
 ### 2.3 一致性与回补