feat(API-AI-081): add KnowledgeItem.sourceId FK to KnowledgeSource

- Prisma schema: add sourceId field + @relation to KnowledgeSource
- KnowledgeSource: add items[] reverse relation + @index on sourceId
- KnowledgeItemsRepository: accept sourceId in create()
- ImportCandidateService.accept(): pass sourceId to create()
- DocumentImport worker: pass sourceId alongside sourceRef

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

prisma/schema.prisma

@@ -247,6 +247,7 @@ model KnowledgeItem {
   content               String?   @db.LongText
   summary               String?   @db.Text
   learnable             Boolean   @default(true)
+  sourceId              String?
   sourceType            String?   @db.VarChar(32)
   sourceRef             String?   @db.VarChar(500)
   sourceDeleted         Boolean   @default(false)
@@ -262,6 +263,7 @@ model KnowledgeItem {
 
   user          User               @relation(fields: [userId], references: [id])
   knowledgeBase KnowledgeBase      @relation(fields: [knowledgeBaseId], references: [id])
+  source        KnowledgeSource?   @relation(fields: [sourceId], references: [id])
   parent        KnowledgeItem?     @relation("KnowledgeItemRelations", fields: [parentId], references: [id])
   children      KnowledgeItem[]    @relation("KnowledgeItemRelations")
   tags          KnowledgeItemTag[]
@@ -270,6 +272,7 @@ model KnowledgeItem {
   @@index([knowledgeBaseId])
   @@index([parentId])
   @@index([itemType])
+  @@index([sourceId])
 }
 
 model KnowledgeItemRelation {
@@ -881,6 +884,7 @@ model KnowledgeSource {
   knowledgeBase KnowledgeBase     @relation(fields: [knowledgeBaseId], references: [id])
   file          UploadedFile?     @relation(fields: [fileId], references: [id])
   chunks        KnowledgeChunk[]
+  items         KnowledgeItem[]
   imports       DocumentImport[]
   references    SourceReference[]
   candidates    ImportCandidate[]

src/modules/import-candidate/import-candidate.service.ts

@@ -38,12 +38,14 @@ export class ImportCandidateService {
     await this.repository.updateStatus(id, 'ACCEPTED');
 
     // 生成 KnowledgeItem，关联到来源
+    const sourceId = (candidate as any).sourceId ?? null;
     await this.itemsRepo.create(candidate.userId, candidate.knowledgeBaseId, {
       title: candidate.title,
       content: (candidate.content as string) ?? '',
       itemType: 'ai_generated',
       orderIndex: candidate.orderIndex,
-      sourceRef: (candidate as any).sourceId ?? null,
+      sourceId,
+      sourceRef: sourceId,
     });
 
     return { status: 'ACCEPTED' };

src/modules/knowledge-items/knowledge-items.repository.ts

@@ -49,6 +49,7 @@ export class KnowledgeItemsRepository {
     content?: string;
     parentId?: string;
     itemType?: string;
+    sourceId?: string;
     sourceType?: string;
     sourceRef?: string;
     durationSeconds?: number;
@@ -65,6 +66,7 @@ export class KnowledgeItemsRepository {
         parentId: dto.parentId ?? null,
         itemType: dto.itemType ?? 'lesson',
         sourceType,
+        sourceId: dto.sourceId ?? null,
         sourceRef: dto.sourceRef ?? null,
         durationSeconds: dto.durationSeconds ?? 0,
         fileSize: dto.fileSize ?? null,

src/workers/document-import.worker.ts

@@ -69,6 +69,7 @@ export class DocumentImportWorker extends WorkerHost {
             content: kp.content,
             itemType: 'lesson',
             orderIndex: kp.suggestedOrder ?? i + 1,
+            sourceId: sourceId,
             sourceRef: sourceId,
           });
         }