feat(memory): add emotion batch extraction task and improve extraction prompts

- Add extract_emotion_batch_task for async emotion extraction
- Refine Chinese entity types and relation types in extraction prompts
- Add STATEMENT_EMOTION_UPDATE Cypher query for Neo4j backfill
- Refactor statement_step and triplet_step implementations

api/app/repositories/neo4j/cypher_queries.py

@@ -46,6 +46,15 @@ SET s += {
 RETURN s.id AS uuid
 """
 
+STATEMENT_EMOTION_UPDATE = """
+UNWIND $items AS item
+MATCH (s:Statement {id: item.statement_id})
+SET s.emotion_type = item.emotion_type,
+    s.emotion_intensity = item.emotion_intensity,
+    s.emotion_keywords = item.emotion_keywords
+RETURN s.id AS uuid
+"""
+
 CHUNK_NODE_SAVE = """
 UNWIND $chunks AS chunk
 MERGE (c:Chunk {id: chunk.id})