feat(admin): LLM config, knowledge base, and WeCom AI binding

Add owner-scoped model API settings, uploadable knowledge bases, and WeCom bot AI/KB wiring with OpenAI-compatible URL normalization.

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

server/dukang-api/src/integrations/llm/knowledge-retrieval.service.ts

@@ -0,0 +1,68 @@
+import { Injectable } from '@nestjs/common';
+import { PrismaService } from '../../common/prisma/prisma.module';
+
+const MAX_CONTEXT_CHARS = 6000;
+
+@Injectable()
+export class KnowledgeRetrievalService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  /** 简易关键词命中：按文档正文包含查询词打分，拼进上下文 */
+  async buildContext(knowledgeBaseId: bigint, query: string): Promise<string> {
+    const kb = await this.prisma.knowledgeBase.findUnique({
+      where: { id: knowledgeBaseId },
+      select: { id: true, enabled: true, name: true },
+    });
+    if (!kb?.enabled) return '';
+
+    const docs = await this.prisma.knowledgeDocument.findMany({
+      where: {
+        knowledgeBaseId,
+        status: 'READY',
+        contentText: { not: null },
+      },
+      select: { title: true, contentText: true },
+      take: 50,
+    });
+    if (!docs.length) return '';
+
+    const tokens = tokenize(query);
+    const scored = docs
+      .map((d) => {
+        const body = d.contentText || '';
+        let score = 0;
+        for (const t of tokens) {
+          if (body.includes(t) || d.title.includes(t)) score += 1;
+        }
+        if (!tokens.length) score = 1;
+        return { title: d.title, body, score };
+      })
+      .filter((x) => x.score > 0)
+      .sort((a, b) => b.score - a.score);
+
+    const picked = scored.length ? scored.slice(0, 5) : docs.slice(0, 3).map((d) => ({
+      title: d.title,
+      body: d.contentText || '',
+      score: 0,
+    }));
+
+    let out = `【知识库：${kb.name}】\n`;
+    for (const p of picked) {
+      const chunk = `### ${p.title}\n${p.body}\n\n`;
+      if (out.length + chunk.length > MAX_CONTEXT_CHARS) {
+        out += chunk.slice(0, Math.max(0, MAX_CONTEXT_CHARS - out.length));
+        break;
+      }
+      out += chunk;
+    }
+    return out.trim();
+  }
+}
+
+function tokenize(q: string): string[] {
+  return q
+    .split(/[\s,，。；;、！？!?\-_/\\]+/)
+    .map((s) => s.trim().toLowerCase())
+    .filter((s) => s.length >= 2)
+    .slice(0, 12);
+}