feat(ai): 页面可配置云端或本地 OpenAI 兼容模型

- 新增 AIConfig 模型（每组织一份，迁移 0005）与 /api/ai-config、
  /api/ai-models 接口；密钥只存后端、读取脱敏、修改记审计
- 支持 OpenAI 及本地 OpenAI 兼容服务（Ollama/LM Studio/vLLM），
  可从 /v1/models 一键获取模型列表多选一；数据库配置优先于环境变量
- 助手调用走生效配置，Copilot 文案同步更新
- 全权限管理员可在「管理 → AI 模型」配置；补接口级测试

finance/views.py

@@ -24,7 +24,7 @@ from openpyxl.cell import WriteOnlyCell
 
 from .analysis import METRICS, analyze, context, default_preferences, dimensions, scoped_facts
 from .importing import file_digest, profile_file, suggest_mapping, validate_mapping
-from .models import Audit, Dataset, Investigation, Membership, Preference, Throttle
+from .models import AIConfig, Audit, Dataset, Investigation, Membership, Preference, Throttle
 
 
 class APIError(Exception):
@@ -130,10 +130,20 @@ def serialize_dataset(ds, detailed=False, restricted=False, raw_access=True):
 
 @endpoint(public=True)
 def session(request):
+    ai_enabled = settings.AI_ENABLED and bool(settings.OPENAI_API_KEY and settings.OPENAI_MODEL)
+    if request.user.is_authenticated:
+        try:
+            cfg = AIConfig.objects.filter(organization=request.user.membership.organization).first()
+            if cfg:
+                ai_enabled = (
+                    cfg.enabled and bool(cfg.model) and (cfg.provider == "local" or bool(cfg.api_key))
+                )
+        except Membership.DoesNotExist:
+            pass
     data = {
         "csrf": get_token(request),
         "user": None,
-        "ai_enabled": settings.AI_ENABLED and bool(settings.OPENAI_API_KEY and settings.OPENAI_MODEL),
+        "ai_enabled": ai_enabled,
     }
     if request.user.is_authenticated:
         try: