feat(onboarding): 新手引导完成按 设备+账号 去重(表/模型/仓储/端点/迁移/测试)

- onboarding_completion 表(user_id+device_id 唯一约束)+ model + repository
- POST /api/v1/user/onboarding/complete 标记完成;登录响应 TokenWithUser.onboarding_completed
  (按登录请求带的 device_id 判定是否已走过引导,跨卸载重装稳定)
- alembic 迁移 onboarding_completion(rebase 到最新 main 后已链在 coupon_daily_completion 之后,单 head)
- docs/database 文档 + tests/test_onboarding.py + run.bat(本地启动脚本)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

run.bat

@@ -0,0 +1,35 @@
+@echo off
+REM Local dev startup script (Windows) - mirror of run.sh
+REM
+REM Usage:
+REM   cd shaguabijia-app-server
+REM   run.bat
+REM
+REM Listens on 0.0.0.0:8770 (works for both real device via adb reverse
+REM and LAN). Auto-reload on code change.
+REM
+REM Prerequisite (first time):
+REM   conda activate pricebot ^&^& pip install -e .
+REM   copy .env.example .env  ^&^& fill JWT_SECRET_KEY
+REM
+REM This file is the Windows-native peer of run.sh. Keeping run.sh untouched
+REM avoids CRLF/encoding fights every time someone bash-runs the .sh on Win.
+
+cd /d "%~dp0"
+
+if not exist .env (
+    echo [X] Missing .env. Run: copy .env.example .env  and fill JWT_SECRET_KEY ^(plus MT_CPS_* if you test Meituan^)
+    exit /b 1
+)
+
+if not exist data mkdir data
+
+REM Build/upgrade SQLite schema (idempotent; no-op if already at head)
+call alembic upgrade head
+if errorlevel 1 (
+    echo [X] alembic upgrade head failed
+    exit /b %errorlevel%
+)
+
+REM Long-running foreground process. Ctrl+C to stop.
+uvicorn app.main:app --host 0.0.0.0 --port 8770 --reload