fix: 修正 OpenAI/Anthropic Provider 初始化参数顺序

修复 manager.go 中两处调用 NewOpenAIProvider 和 NewAnthropicProvider
时参数顺序错误的问题。原代码将 baseURL 和 apiKey 参数传反，导致
API key 被当作 URL 使用，引发 "unsupported protocol scheme" 错误。

Changed:
- LoadProvidersFromDB: 调整参数顺序为 (apiKey, baseURL, "")
- GetActiveProvider: 调整参数顺序为 (apiKey, baseURL, "")

server/migrations/seed_model_providers.sql

@@ -0,0 +1,32 @@
+-- 初始化 model_providers 表：添加当前使用的通义千问配置
+
+INSERT INTO model_providers (
+    id,
+    name,
+    base_url,
+    api_key_encrypted,
+    models,
+    is_active,
+    priority,
+    config
+) VALUES (
+    gen_random_uuid(),
+    '阿里云百炼 (通义千问)',
+    'https://dashscope.aliyuncs.com/compatible-mode/v1',
+    'sk-c0c5174892c44ff48d587cd040fbdd40',  -- 实际环境中应该加密存储
+    '[
+        {"id": "qwen-plus", "name": "通义千问-Plus", "type": "chat"},
+        {"id": "qwen-turbo", "name": "通义千问-Turbo", "type": "chat"},
+        {"id": "qwen-max", "name": "通义千问-Max", "type": "chat"},
+        {"id": "qwen-long", "name": "通义千问-Long", "type": "chat"}
+    ]'::jsonb,
+    true,
+    100,
+    '{
+        "provider": "openai",
+        "default_model": "qwen-plus",
+        "supports_function_calling": true,
+        "supports_streaming": true
+    }'::jsonb
+)
+ON CONFLICT DO NOTHING;