feat(#69): implement embedding generation pipeline

Generate embeddings for knowledge entries using Ollama via BullMQ job queue.

Changes:
- Created OllamaEmbeddingService for Ollama-based embedding generation
- Set up BullMQ queue and processor for async embedding jobs
- Integrated queue into knowledge entry lifecycle (create/update)
- Added rate limiting (1 job/second) and retry logic (3 attempts)
- Added OLLAMA_EMBEDDING_MODEL environment variable configuration
- Implemented dimension normalization (padding/truncating to 1536 dimensions)
- Added graceful degradation when Ollama is unavailable

Test Coverage:
- All 31 embedding-related tests passing
- ollama-embedding.service.spec.ts: 13 tests
- embedding-queue.spec.ts: 6 tests
- embedding.processor.spec.ts: 5 tests
- Build and linting successful

Fixes #69

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/api/src/knowledge/knowledge.module.ts

@@ -1,6 +1,8 @@
 import { Module } from "@nestjs/common";
+import { BullModule } from "@nestjs/bullmq";
 import { PrismaModule } from "../prisma/prisma.module";
 import { AuthModule } from "../auth/auth.module";
+import { OllamaModule } from "../ollama/ollama.module";
 import { KnowledgeService } from "./knowledge.service";
 import {
   KnowledgeController,
@@ -18,9 +20,26 @@ import {
   KnowledgeCacheService,
   EmbeddingService,
 } from "./services";
+import { OllamaEmbeddingService } from "./services/ollama-embedding.service";
+import { EmbeddingQueueService } from "./queues/embedding-queue.service";
+import { EmbeddingProcessor } from "./queues/embedding.processor";
 
 @Module({
-  imports: [PrismaModule, AuthModule],
+  imports: [
+    PrismaModule,
+    AuthModule,
+    OllamaModule,
+    BullModule.registerQueue({
+      name: "embeddings",
+      defaultJobOptions: {
+        attempts: 3,
+        backoff: {
+          type: "exponential",
+          delay: 5000,
+        },
+      },
+    }),
+  ],
   controllers: [
     KnowledgeController,
     KnowledgeCacheController,
@@ -37,7 +56,17 @@ import {
     StatsService,
     KnowledgeCacheService,
     EmbeddingService,
+    OllamaEmbeddingService,
+    EmbeddingQueueService,
+    EmbeddingProcessor,
+  ],
+  exports: [
+    KnowledgeService,
+    LinkResolutionService,
+    SearchService,
+    EmbeddingService,
+    OllamaEmbeddingService,
+    EmbeddingQueueService,
   ],
-  exports: [KnowledgeService, LinkResolutionService, SearchService, EmbeddingService],
 })
 export class KnowledgeModule {}