feat: DB WAL 모드 적용, .env.example 정리 (#210, #213, #216)

- #210: init_db()에 WAL 저널 모드 적용 (파일 DB에만, :memory: 제외)
  - 대시보드(READ)와 거래루프(WRITE) 동시 접근 시 SQLite 락 오류 방지
  - busy_timeout=5000ms 설정
- #213: RATE_LIMIT_RPS 기본값 2.0으로 통일 (.env.example이 5.0으로 잘못 표기됨)
- #216: .env.example 중요 변수 추가 및 정리
  - KIS_BASE_URL 모의/실전 URL 주석 명시 (포트 29443 수정 포함)
  - MODE, TRADE_MODE, ENABLED_MARKETS, PAPER_OVERSEAS_CASH 추가
  - GEMINI_MODEL 업데이트 (gemini-pro → gemini-2.0-flash-exp)
  - DASHBOARD 설정 섹션 추가

테스트 2개 추가 (WAL 파일 DB 적용, 메모리 DB 미적용 검증)

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

.env.example

@@ -1,36 +1,82 @@
+# ============================================================
+# The Ouroboros — Environment Configuration
+# ============================================================
+# Copy this file to .env and fill in your values.
+# Lines starting with # are comments.
+
+# ============================================================
 # Korea Investment Securities API
+# ============================================================
 KIS_APP_KEY=your_app_key_here
 KIS_APP_SECRET=your_app_secret_here
 KIS_ACCOUNT_NO=12345678-01
-KIS_BASE_URL=https://openapivts.koreainvestment.com:9443
 
+# Paper trading (VTS): https://openapivts.koreainvestment.com:29443
+# Live trading:        https://openapi.koreainvestment.com:9443
+KIS_BASE_URL=https://openapivts.koreainvestment.com:29443
+
+# ============================================================
+# Trading Mode
+# ============================================================
+# paper = 모의투자 (safe for testing), live = 실전투자 (real money)
+MODE=paper
+
+# daily = batch per session, realtime = per-stock continuous scan
+TRADE_MODE=daily
+
+# Comma-separated market codes: KR, US, JP, HK, CN, VN
+ENABLED_MARKETS=KR,US
+
+# Simulated USD cash for paper (VTS) overseas trading.
+# VTS overseas balance API often returns 0; this value is used as fallback.
+# Set to 0 to disable fallback (not used in live mode).
+PAPER_OVERSEAS_CASH=50000.0
+
+# ============================================================
 # Google Gemini
+# ============================================================
 GEMINI_API_KEY=your_gemini_api_key_here
-GEMINI_MODEL=gemini-pro
+# Recommended: gemini-2.0-flash-exp or gemini-1.5-pro
+GEMINI_MODEL=gemini-2.0-flash-exp
 
+# ============================================================
 # Risk Management
+# ============================================================
 CIRCUIT_BREAKER_PCT=-3.0
 FAT_FINGER_PCT=30.0
 CONFIDENCE_THRESHOLD=80
 
+# ============================================================
 # Database
+# ============================================================
 DB_PATH=data/trade_logs.db
 
-# Rate Limiting (requests per second for KIS API)
-# Reduced to 5.0 to avoid "초당 거래건수 초과" errors (EGW00201)
-RATE_LIMIT_RPS=5.0
+# ============================================================
+# Rate Limiting
+# ============================================================
+# KIS API real limit is ~2 RPS. Keep at 2.0 for maximum safety.
+# Increasing this risks EGW00201 "초당 거래건수 초과" errors.
+RATE_LIMIT_RPS=2.0
 
-# Trading Mode (paper / live)
-MODE=paper
-
-# External Data APIs (optional — for enhanced decision-making)
+# ============================================================
+# External Data APIs (optional)
+# ============================================================
 # NEWS_API_KEY=your_news_api_key_here
 # NEWS_API_PROVIDER=alphavantage
 # MARKET_DATA_API_KEY=your_market_data_key_here
 
+# ============================================================
 # Telegram Notifications (optional)
+# ============================================================
 # Get bot token from @BotFather on Telegram
 # Get chat ID from @userinfobot or your chat
 # TELEGRAM_BOT_TOKEN=1234567890:ABCdefGHIjklMNOpqrsTUVwxyz
 # TELEGRAM_CHAT_ID=123456789
 # TELEGRAM_ENABLED=true
+
+# ============================================================
+# Dashboard (optional)
+# ============================================================
+# DASHBOARD_ENABLED=false
+# DASHBOARD_HOST=127.0.0.1
+# DASHBOARD_PORT=8080

src/db.py

@@ -14,6 +14,11 @@ def init_db(db_path: str) -> sqlite3.Connection:
     if db_path != ":memory:":
         Path(db_path).parent.mkdir(parents=True, exist_ok=True)
     conn = sqlite3.connect(db_path)
+    # Enable WAL mode for concurrent read/write (dashboard + trading loop).
+    # WAL does not apply to in-memory databases.
+    if db_path != ":memory:":
+        conn.execute("PRAGMA journal_mode=WAL")
+        conn.execute("PRAGMA busy_timeout=5000")
     conn.execute(
         """
         CREATE TABLE IF NOT EXISTS trades (

tests/test_db.py

@@ -1,5 +1,8 @@
 """Tests for database helper functions."""
 
+import tempfile
+import os
+
 from src.db import get_open_position, init_db, log_trade
 
 
@@ -58,3 +61,37 @@ def test_get_open_position_returns_none_when_latest_is_sell() -> None:
 def test_get_open_position_returns_none_when_no_trades() -> None:
     conn = init_db(":memory:")
     assert get_open_position(conn, "AAPL", "US_NASDAQ") is None
+
+
+# ---------------------------------------------------------------------------
+# WAL mode tests (issue #210)
+# ---------------------------------------------------------------------------
+
+
+def test_wal_mode_applied_to_file_db() -> None:
+    """File-based DB must use WAL journal mode for dashboard concurrent reads."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        db_path = f.name
+    try:
+        conn = init_db(db_path)
+        cursor = conn.execute("PRAGMA journal_mode")
+        mode = cursor.fetchone()[0]
+        assert mode == "wal", f"Expected WAL mode, got {mode}"
+        conn.close()
+    finally:
+        os.unlink(db_path)
+        # Clean up WAL auxiliary files if they exist
+        for ext in ("-wal", "-shm"):
+            path = db_path + ext
+            if os.path.exists(path):
+                os.unlink(path)
+
+
+def test_wal_mode_not_applied_to_memory_db() -> None:
+    """:memory: DB must not apply WAL (SQLite does not support WAL for in-memory)."""
+    conn = init_db(":memory:")
+    cursor = conn.execute("PRAGMA journal_mode")
+    mode = cursor.fetchone()[0]
+    # In-memory DBs default to 'memory' journal mode
+    assert mode != "wal", "WAL should not be set on in-memory database"
+    conn.close()