feat(project): 初始化项目结构和配置

- 添加.gitignore和.flaskenv环境配置文件
- 创建Flask应用基础架构，包括models、services、utils模块
- 配置数据库模型User和Setting，集成SQLAlchemy和Alembic迁移
- 添加前端Vue项目结构，包含Element Plus组件库
- 配置前后端API路由和蓝prints模块
- 实现书籍下载服务BookService功能模块
- 添加代码规范配置.editorconfig、.oxfmtrc.json、.oxlintrc.json
- 配置VSCode推荐插件和前端构建工具链
- 实现文件服务FileService和相关业务逻辑

migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}