feat(rag): phase35 ivfflat 向量索引 — 5814 chunks 已建立

已在 prod 執行: idx_rag_chunks_embedding (lists=100, cosine)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/migrations/phase35_rag_ivfflat_index.sql

@@ -0,0 +1,14 @@
+-- Phase 35: RAG ivfflat 向量索引
+-- 前提: rag_chunks 已有 2582+ chunks
+-- 執行: psql awoooi_prod
+-- 2026-04-10 Claude Sonnet 4.6 Asia/Taipei
+
+CREATE INDEX IF NOT EXISTS idx_rag_chunks_embedding
+  ON rag_chunks
+  USING ivfflat (embedding vector_cosine_ops)
+  WITH (lists = 100);
+
+-- 驗證
+SELECT indexname, indexdef
+FROM pg_indexes
+WHERE tablename = 'rag_chunks' AND indexname = 'idx_rag_chunks_embedding';