fix: 导入 Career 和 CharacterCareer 模型确保职业系统表自动创建

- 修复：Career 和 CharacterCareer 模型未被导入，导致新用户部署时这些表无法自动创建
- 修复：新用户创建角色时会因为 main_career_id 字段缺失而报错
- 现在 SQLAlchemy 会在首次启动时自动创建职业系统所需的所有表
- 这确保新用户部署时不会遇到数据库迁移问题

backend/app/database.py

@@ -21,7 +21,7 @@ from app.models import (
     Settings, WritingStyle, ProjectDefaultStyle,
     RelationshipType, CharacterRelationship, Organization, OrganizationMember,
     StoryMemory, PlotAnalysis, AnalysisTask, BatchGenerationTask,
-    RegenerationTask
+    RegenerationTask, Career, CharacterCareer
 )
 
 # 引擎缓存：每个用户一个引擎

backend/app/models/__init__.py

@@ -14,6 +14,7 @@ from app.models.project_default_style import ProjectDefaultStyle
 from app.models.mcp_plugin import MCPPlugin
 from app.models.user import User, UserPassword
 from app.models.regeneration_task import RegenerationTask
+from app.models.career import Career, CharacterCareer
 
 __all__ = [
     "Project",
@@ -35,5 +36,7 @@ __all__ = [
     "MCPPlugin",
     "User",
     "UserPassword",
-    "RegenerationTask"
+    "RegenerationTask",
+    "Career",
+    "CharacterCareer"
 ]