feat: 支持 ONLYOFFICE 持久化配置管理

- 添加 SettingsRenderForm schema 和 renderForm 字段
- 实现数据库 schema 自动迁移（onlyoffice_enabled, onlyoffice_public_url, onlyoffice_jwt_secret_encrypted）
- 新增 resolve_onlyoffice_settings() 函数支持运行时配置解析
- 知识库服务改用数据库配置替代运行时配置
- 前端添加文件渲染配置页面，支持 JWT 密钥管理
- 完善相关测试覆盖

server/src/app/schemas/settings.py

@@ -110,6 +110,20 @@ class SettingsLogForm(BaseModel):
         return value.strip()
 
 
+class SettingsRenderForm(BaseModel):
+    enabled: bool = False
+    publicUrl: str = Field(default="", max_length=512)
+    jwtSecret: str = Field(default="", max_length=1024)
+    jwtSecretConfigured: bool = False
+
+    @field_validator("publicUrl", "jwtSecret", mode="before")
+    @classmethod
+    def strip_string(cls, value: str | None) -> str | None:
+        if value is None:
+            return None
+        return value.strip()
+
+
 class SettingsMailForm(BaseModel):
     smtpHost: str = Field(min_length=1, max_length=255)
     port: int = Field(default=465, ge=1, le=65535)
@@ -146,6 +160,7 @@ class SettingsRead(BaseModel):
     companyForm: SettingsCompanyForm
     adminForm: SettingsAdminForm
     llmForm: SettingsLlmForm
+    renderForm: SettingsRenderForm
     logForm: SettingsLogForm
     mailForm: SettingsMailForm
 
@@ -154,6 +169,7 @@ class SettingsWrite(BaseModel):
     companyForm: SettingsCompanyForm
     adminForm: SettingsAdminForm
     llmForm: SettingsLlmForm
+    renderForm: SettingsRenderForm
     logForm: SettingsLogForm
     mailForm: SettingsMailForm