feat(db): P1 Alembic+模型整合 — 唯一总库基线迁移 + 培训/园区 ORM 模型

- 新增 alembic（ini/env async/script.mako/versions/0001_initial）。
- models.py 并入培训表(training_accounts/events/bookings/tests/courses/policy/plan/survey_logs)
  与园区表(park_tenants/companies/kb_docs/screens)，与平台同库、命名加域前缀避免撞名。
- baseline 迁移用 create_all(幂等)：既有平台表保留，新增培训/园区表被建。
- 验证：对临时库 uv run alembic upgrade head 建出全部新表。

alembic.ini

@@ -0,0 +1,39 @@
+[alembic]
+script_location = alembic
+prepend_sys_path = .
+# 数据库 URL 由 alembic/env.py 从服务端配置读取（config.DATABASE_URL），此处仅占位
+sqlalchemy.url = sqlite+aiosqlite:///serverdata/data/app.db
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S