refactor: 重构代码生成模板与项目结构，新增发票PDF生成功能

1.  统一移动代码生成模板到根目录templates目录，删除旧模板文件
2.  调整SQLAlchemy导入顺序，优化代码格式
3.  重构查询参数类，复用BaseQueryParam基础能力
4.  新增发票管理模块：添加weasyprint依赖，实现本地PDF发票渲染
5.  完善邮件、菜单等模块的代码实现与注释
6.  修复SQL查询条件写法，使用is_(True)替代==True
7.  补全模型类的UserMixin、TenantMixin继承与配置

backend/templates/python/schema.py.j2

@@ -0,0 +1,87 @@
+# -*- coding: utf-8 -*-
+
+{% if table.sub %}
+from typing import List
+{% endif %}
+from pydantic import BaseModel, ConfigDict, Field
+from fastapi import Query
+{% for import_stmt in schema_import_list %}
+{{ import_stmt }}
+{% endfor %}
+{# DateTimeStr 由 schema_import_list 在存在 created_time/updated_time 列时注入 #}
+from app.common.enums import QueueEnum
+from app.core.base_schema import BaseSchema, UserBySchema
+
+class {{ class_name }}CreateSchema(BaseModel):
+    """
+    {{ function_name }}新增模型
+    """
+    {% for column in columns %}
+    {% if column.column_name not in ['uuid', 'created_time', 'updated_time', 'created_id', 'updated_id', 'is_deleted', 'deleted_time', 'deleted_id'] and column.column_name != pk_column_name %}
+    {% if column.column_name == 'status' %}
+    {{ column.column_name }}: {{ column.python_type }} = Field(default="0", description='{{ column.column_comment }}')
+    {% elif column.column_name == 'description' %}
+    {{ column.column_name }}: str | None = Field(default=None, max_length=255, description='{{ column.column_comment }}')
+    {% else %}
+    {{ column.column_name }}: {{ column.python_type }} = Field(default=..., description='{{ column.column_comment }}')
+    {% endif %}
+    {% endif %}
+    {% endfor %}
+
+
+class {{ class_name }}UpdateSchema({{ class_name }}CreateSchema):
+    """
+    {{ function_name }}更新模型
+    """
+    ...
+
+
+class {{ class_name }}OutSchema({{ class_name }}CreateSchema, BaseSchema, UserBySchema):
+    """
+    {{ function_name }}响应模型
+    """
+    model_config = ConfigDict(from_attributes=True)
+
+
+class {{ class_name }}QueryParam:
+    """{{ function_name }}查询参数"""
+
+    def __init__(
+        self,
+        {% for column in columns %}
+        {% if column.is_query and column.query_type == 'LIKE' %}
+        {{ column.column_name }}: str | None = Query(None, description="{{ column.column_comment }}"),
+        {% endif %}
+        {% endfor %}
+        {% for column in columns %}
+        {% if column.is_query and column.query_type == 'EQ' and column.column_name not in ['created_time', 'updated_time'] %}
+        {{ column.column_name }}: {{ column.python_type }} | None = Query(None, description="{{ column.column_comment }}"),
+        {% endif %}
+        {% endfor %}
+        {% if 'created_time' in table_column_names %}
+        created_time: list[DateTimeStr] | None = Query(None, description="创建时间范围", examples=["2025-01-01 00:00:00", "2025-12-31 23:59:59"]),
+        {% endif %}
+        {% if 'updated_time' in table_column_names %}
+        updated_time: list[DateTimeStr] | None = Query(None, description="更新时间范围", examples=["2025-01-01 00:00:00", "2025-12-31 23:59:59"]),
+        {% endif %}
+    ) -> None:
+        {% for column in columns %}
+        {% if column.is_query and column.query_type == 'LIKE' %}
+        # 模糊查询字段
+        self.{{ column.column_name }} = (QueueEnum.like.value, {{ column.column_name }})
+        {% elif column.is_query and column.query_type == 'EQ' and column.column_name not in ['created_time', 'updated_time'] %}
+        # 精确查询字段
+        if {{ column.column_name }} is not None:
+            self.{{ column.column_name }} = (QueueEnum.eq.value, {{ column.column_name }})
+        {% endif %}
+        {% endfor %}
+        {% if 'created_time' in table_column_names %}
+        # 时间范围查询
+        if created_time and len(created_time) == 2:
+            self.created_time = (QueueEnum.between.value, (created_time[0], created_time[1]))
+        {% endif %}
+        {% if 'updated_time' in table_column_names %}
+        if updated_time and len(updated_time) == 2:
+            self.updated_time = (QueueEnum.between.value, (updated_time[0], updated_time[1]))
+        {% endif %}
+        {# created_id / updated_id 若为 EQ 查询列，已在上方 query_type 循环中处理 #}