feat: M2-06 — Artifact model + KnowledgeItem.learnable + Admin AAPI

- Artifact base model for future FlashcardSet/Quiz/StudyGuide
- KnowledgeItem.learnable boolean (default true) for M3 LearningSession
- Admin AAPI: GET candidates (by status/kbId), GET items (by kbId)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

prisma/migrations/20260525040000_add_artifact_learnable/migration.sql

@@ -0,0 +1,16 @@
+ALTER TABLE `KnowledgeItem` ADD COLUMN `learnable` BOOLEAN NOT NULL DEFAULT true;
+
+CREATE TABLE IF NOT EXISTS `Artifact` (
+    `id` VARCHAR(191) NOT NULL,
+    `userId` VARCHAR(191) NOT NULL,
+    `kbId` VARCHAR(191) NOT NULL,
+    `type` VARCHAR(32) NOT NULL,
+    `title` VARCHAR(255) NOT NULL,
+    `configJson` JSON NULL,
+    `status` VARCHAR(16) NOT NULL DEFAULT 'draft',
+    `createdAt` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
+    `updatedAt` DATETIME(3) NOT NULL,
+    INDEX `Artifact_userId_idx`(`userId`),
+    INDEX `Artifact_kbId_idx`(`kbId`),
+    PRIMARY KEY (`id`)
+) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

prisma/schema.prisma

@@ -185,6 +185,21 @@ model KnowledgeBase {
   @@index([status])
 }
 
+model Artifact {
+  id         String   @id @default(cuid())
+  userId     String
+  kbId       String
+  type       String   @db.VarChar(32)
+  title      String   @db.VarChar(255)
+  configJson Json?
+  status     String   @default("draft") @db.VarChar(16)
+  createdAt  DateTime @default(now())
+  updatedAt  DateTime @updatedAt
+
+  @@index([userId])
+  @@index([kbId])
+}
+
 model KnowledgeItem {
   id                  String    @id @default(cuid())
   userId              String
@@ -194,6 +209,7 @@ model KnowledgeItem {
   title               String    @db.VarChar(255)
   content             String?   @db.LongText
   summary             String?   @db.Text
+  learnable           Boolean   @default(true)
   sourceType          String?   @db.VarChar(32)
   sourceRef           String?   @db.VarChar(500)
   sourceDeleted       Boolean   @default(false)

src/modules/admin-knowledge/admin-knowledge.controller.ts

@@ -67,4 +67,25 @@ export class AdminKnowledgeController {
       take: 50,
     });
   }
+
+  // ── Candidates ──
+
+  @Get('candidates')
+  @ApiOperation({ summary: '候选知识点列表' })
+  async candidates(@Query('status') status?: string, @Query('kbId') kbId?: string) {
+    const where: any = {};
+    if (status) where.status = status;
+    if (kbId) where.knowledgeBaseId = kbId;
+    return this.prisma.importCandidate.findMany({ where, orderBy: { createdAt: 'desc' }, take: 100 });
+  }
+
+  // ── Knowledge items ──
+
+  @Get('items')
+  @ApiOperation({ summary: '知识点列表（管理员）' })
+  async items(@Query('kbId') kbId?: string, @Query('limit') limit = '50') {
+    const where: any = { deletedAt: null };
+    if (kbId) where.knowledgeBaseId = kbId;
+    return this.prisma.knowledgeItem.findMany({ where, orderBy: { createdAt: 'desc' }, take: parseInt(limit) });
+  }
 }