Add EmbeddingService using OpenAI-compatible embeddings API (supports text-embedding-3-small, configurable via EMBEDDING_MODEL and EMBEDDING_API_URL env vars). Wire embedding generation into insight creation and semantic search endpoint. POST /api/memory/search now generates a query embedding and performs cosine distance search via pgvector when OPENAI_API_KEY is configured. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>