feat(provider): add required field validation with toast notifications

- Add validation for provider name (required for all providers)
- Add validation for API endpoint and API Key (required for non-official providers)
- Use toast notifications instead of inline form errors for better visibility
- Move name validation from zod schema to handleSubmit for consistent UX
- Add i18n keys: endpointRequired, apiKeyRequired

src/i18n/locales/en.json

@@ -275,6 +275,8 @@
     "fillConfigContent": "Please fill in configuration content",
     "fillParameter": "Please fill in {{label}}",
     "fillTemplateValue": "Please fill in {{label}}",
+    "endpointRequired": "API endpoint is required for non-official providers",
+    "apiKeyRequired": "API Key is required for non-official providers",
     "configJsonError": "Config JSON format error, please check syntax",
     "authJsonRequired": "auth.json must be a JSON object",
     "authJsonError": "auth.json format error, please check JSON syntax",

src/i18n/locales/zh.json

@@ -275,6 +275,8 @@
     "fillConfigContent": "请填写配置内容",
     "fillParameter": "请填写 {{label}}",
     "fillTemplateValue": "请填写 {{label}}",
+    "endpointRequired": "非官方供应商请填写 API 端点",
+    "apiKeyRequired": "非官方供应商请填写 API Key",
     "configJsonError": "配置JSON格式错误，请检查语法",
     "authJsonRequired": "auth.json 必须是 JSON 对象",
     "authJsonError": "auth.json 格式错误，请检查JSON语法",