Implement Phase 4~14: LangGraph Agent, RAG pipeline, Gradio Web UI, voice interface

- Upgrade LLM to Qwen3-14B-4bit with Thinking mode (MlxChatModel as LangChain BaseChatModel)
- Add LangGraph ReAct agent with tool calling loop (search_documents, web_search, get_current_date, remember/recall_user_info)
- Add RAG pipeline: BAAI/bge-m3 embeddings + Qdrant vector store + semantic chunking (SemanticSplitter via cosine similarity)
- Replace fixed-size RecursiveCharacterTextSplitter with meaning-based SemanticSplitter (numpy only, no extra deps)
- Add Gradio Web UI (app.py): chat, document ingestion, document management tabs
- Add multi-user support (user_id isolation in DB + per-user agent cache + dropdown selector)
- Add conversation history restore from MySQL on agent init (Phase 11)
- Add UserProfileRepository for persistent user profile (remember/recall tools)
- Add thread-local DB connections to fix pymysql thread-safety with LangGraph ToolNode
- Add Phase 14 voice interface: Whisper STT (microphone → text) + macOS TTS (say -v Yuna)
- Enforce search_documents-first policy in system prompt and tool descriptions
- Update ROADMAP2.md: Phase 14 완료, Phase 13 청킹 부분 완료

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

services/db/mysql_service.py

@@ -1,47 +1,81 @@
 from __future__ import annotations
+import threading
 from typing import Any
 
 
 class DatabaseService:
-    """MySQL 연결을 캡슐화하는 서비스. 미설정 시 graceful skip."""
+    """MySQL 연결을 캡슐화하는 서비스. 미설정 시 graceful skip.
 
-    def __init__(self, host: str, port: int, db: str, user: str, password: str):
+    스레드별 독립 연결(thread-local)을 사용해 LangGraph ToolNode의
+    스레드 풀 실행과 pymysql 비안전성 문제를 해결한다.
+    """
+
+    def __init__(
+        self,
+        host: str,
+        port: int,
+        db: str,
+        user: str,
+        password: str,
+    ):
         self._config = dict(host=host, port=port, db=db, user=user, passwd=password)
-        self._conn = None
+        self._local = threading.local()
+
+    # ── DB 연결 ────────────────────────────────────────────────────────
+
+    def _get_conn(self):
+        if not self._config["user"]:
+            return None
+
+        import pymysql
+        conn = getattr(self._local, "conn", None)
+        if conn is None:
+            try:
+                self._local.conn = pymysql.connect(**self._config)
+            except Exception as e:
+                print(f"[DB] 연결 실패: {e}")
+                return None
+        else:
+            try:
+                conn.ping(reconnect=True)
+            except Exception:
+                try:
+                    self._local.conn = pymysql.connect(**self._config)
+                except Exception as e:
+                    print(f"[DB] 재연결 실패: {e}")
+                    return None
+        return self._local.conn
 
     def connect(self) -> None:
-        if not self._config["user"]:
-            return
-        try:
-            import pymysql
-            self._conn = pymysql.connect(**self._config)
-        except Exception as e:
-            print(f"[DB] 연결 실패 (선택적 기능): {e}")
+        self._get_conn()
 
     def execute(self, sql: str, params: tuple = ()) -> list[dict[str, Any]]:
-        if self._conn is None:
+        conn = self._get_conn()
+        if conn is None:
             return []
-        cursor = self._conn.cursor()
+        cursor = conn.cursor()
         cursor.execute(sql, params)
         columns = [d[0] for d in cursor.description or []]
         return [dict(zip(columns, row)) for row in cursor.fetchall()]
 
     def execute_write(self, sql: str, params: tuple = ()) -> int:
-        """INSERT/UPDATE/DELETE 실행 후 lastrowid 반환."""
-        if self._conn is None:
+        conn = self._get_conn()
+        if conn is None:
             return 0
-        cursor = self._conn.cursor()
+        cursor = conn.cursor()
         cursor.execute(sql, params)
-        self._conn.commit()
+        conn.commit()
         return cursor.lastrowid
 
     def init_schema(self) -> None:
-        if self._conn is None:
+        conn = self._get_conn()
+        if conn is None:
             return
-        cursor = self._conn.cursor()
+        cursor = conn.cursor()
         cursor.execute("""
             CREATE TABLE IF NOT EXISTS td_conversations (
                 id INT AUTO_INCREMENT PRIMARY KEY,
+                user_id VARCHAR(50) NOT NULL DEFAULT 'default',
                 created_at DATETIME DEFAULT CURRENT_TIMESTAMP
             )
         """)
@@ -55,9 +89,35 @@ class DatabaseService:
                 FOREIGN KEY (conversation_id) REFERENCES td_conversations(id)
             )
         """)
-        self._conn.commit()
+        cursor.execute("""
+            CREATE TABLE IF NOT EXISTS td_user_profile (
+                id INT AUTO_INCREMENT PRIMARY KEY,
+                user_id VARCHAR(50) NOT NULL DEFAULT 'default',
+                key_name VARCHAR(100) NOT NULL,
+                value TEXT NOT NULL,
+                updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+                UNIQUE KEY uq_user_key (user_id, key_name)
+            )
+        """)
+        conn.commit()
+        self._migrate_schema(conn)
+
+    def _migrate_schema(self, conn) -> None:
+        cursor = conn.cursor()
+        for sql in [
+            "ALTER TABLE td_conversations ADD COLUMN user_id VARCHAR(50) NOT NULL DEFAULT 'default'",
+            "ALTER TABLE td_user_profile ADD COLUMN user_id VARCHAR(50) NOT NULL DEFAULT 'default'",
+            "ALTER TABLE td_user_profile DROP INDEX key_name",
+            "ALTER TABLE td_user_profile ADD UNIQUE KEY uq_user_key (user_id, key_name)",
+        ]:
+            try:
+                cursor.execute(sql)
+                conn.commit()
+            except Exception:
+                pass
 
     def close(self) -> None:
-        if self._conn:
-            self._conn.close()
-            self._conn = None
+        conn = getattr(self._local, "conn", None)
+        if conn:
+            conn.close()
+            self._local.conn = None