feat(API): 添加消息全局搜索接口

- 新增 /api/messages/search 搜索 API
- 支持关键词模糊搜索消息内容
- 支持角色筛选（用户消息/AI回复/全部）
- 支持分页查询，返回结果总数
- 仅查询当前用户的未归档对话

src/app/api/messages/search/route.ts

@@ -0,0 +1,146 @@
+import { NextResponse } from 'next/server';
+import { db } from '@/drizzle/db';
+import { messages, conversations } from '@/drizzle/schema';
+import { getCurrentUser } from '@/lib/auth';
+import { eq, and, ilike, desc, sql, or } from 'drizzle-orm';
+
+/**
+ * 搜索结果类型
+ */
+export interface SearchResult {
+  messageId: string;
+  conversationId: string;
+  conversationTitle: string;
+  role: string;
+  content: string;
+  createdAt: Date;
+}
+
+/**
+ * GET /api/messages/search - 全局消息搜索
+ *
+ * Query Parameters:
+ * - q: string (必填) - 搜索关键词
+ * - role: 'user' | 'assistant' | 'all' (可选) - 角色筛选，默认 'all'
+ * - page: number (可选) - 页码，默认 1
+ * - limit: number (可选) - 每页数量，默认 20，最大 50
+ */
+export async function GET(request: Request) {
+  try {
+    // 验证用户身份
+    const user = await getCurrentUser();
+    if (!user) {
+      return NextResponse.json(
+        { error: '请先登录' },
+        { status: 401 }
+      );
+    }
+
+    // 解析查询参数
+    const { searchParams } = new URL(request.url);
+    const query = searchParams.get('q')?.trim();
+    const role = searchParams.get('role') || 'all';
+    const page = Math.max(1, parseInt(searchParams.get('page') || '1', 10));
+    const limit = Math.min(50, Math.max(1, parseInt(searchParams.get('limit') || '20', 10)));
+    const offset = (page - 1) * limit;
+
+    // 验证搜索关键词
+    if (!query || query.length < 1) {
+      return NextResponse.json(
+        { error: '请输入搜索关键词' },
+        { status: 400 }
+      );
+    }
+
+    // 关键词长度限制
+    if (query.length > 100) {
+      return NextResponse.json(
+        { error: '搜索关键词过长，请限制在 100 字符以内' },
+        { status: 400 }
+      );
+    }
+
+    // 构建搜索条件
+    const searchPattern = `%${query}%`;
+
+    // 基础条件：用户的对话
+    const baseConditions = [
+      eq(conversations.userId, user.userId),
+      eq(conversations.isArchived, false), // 排除已归档对话
+    ];
+
+    // 角色筛选条件
+    const roleCondition = role === 'all'
+      ? or(eq(messages.role, 'user'), eq(messages.role, 'assistant'))
+      : eq(messages.role, role);
+
+    // 内容搜索条件
+    const contentCondition = ilike(messages.content, searchPattern);
+
+    // 执行搜索查询
+    const results = await db
+      .select({
+        messageId: messages.messageId,
+        conversationId: messages.conversationId,
+        conversationTitle: conversations.title,
+        role: messages.role,
+        content: messages.content,
+        createdAt: messages.createdAt,
+      })
+      .from(messages)
+      .innerJoin(
+        conversations,
+        eq(messages.conversationId, conversations.conversationId)
+      )
+      .where(
+        and(
+          ...baseConditions,
+          roleCondition,
+          contentCondition
+        )
+      )
+      .orderBy(desc(messages.createdAt))
+      .limit(limit)
+      .offset(offset);
+
+    // 获取总数（用于分页）
+    const countResult = await db
+      .select({
+        count: sql<number>`count(*)::int`,
+      })
+      .from(messages)
+      .innerJoin(
+        conversations,
+        eq(messages.conversationId, conversations.conversationId)
+      )
+      .where(
+        and(
+          ...baseConditions,
+          roleCondition,
+          contentCondition
+        )
+      );
+
+    const total = countResult[0]?.count || 0;
+    const totalPages = Math.ceil(total / limit);
+
+    return NextResponse.json({
+      success: true,
+      data: {
+        results,
+        total,
+        page,
+        limit,
+        totalPages,
+        query,
+        role,
+      },
+    });
+  } catch (error) {
+    console.error('Search messages error:', error);
+    return NextResponse.json(
+      { error: '搜索失败，请稍后重试' },
+      { status: 500 }
+    );
+  }
+}