feat: Add OpenAI-compatible provider nodes

- Support multiple OpenAI-compatible providers with custom prefix/baseUrl
- Add provider nodes CRUD (create/read/update/delete)
- URL building: baseUrl + /chat/completions or /responses
- Model import from /models endpoint
- API key validation via /models
- Usage type safety across all translators
- OAuth token auto-refresh for expired tokens

src/shared/constants/providers.js

@@ -22,6 +22,12 @@ export const APIKEY_PROVIDERS = {
   gemini: { id: "gemini", alias: "gemini", name: "Gemini", icon: "diamond", color: "#4285F4", textIcon: "GE" },
 };
 
+export const OPENAI_COMPATIBLE_PREFIX = "openai-compatible-";
+
+export function isOpenAICompatibleProvider(providerId) {
+  return typeof providerId === "string" && providerId.startsWith(OPENAI_COMPATIBLE_PREFIX);
+}
+
 // All providers (combined)
 export const AI_PROVIDERS = { ...OAUTH_PROVIDERS, ...APIKEY_PROVIDERS };