feat: add OllamaLocalExecutor and update provider handling

- Introduced OllamaLocalExecutor to handle requests for the "ollama-local" provider.
- Removed the direct URL construction for "ollama-local" from BaseExecutor.
- Updated index.js to include the new OllamaLocalExecutor in the executors mapping.
- Enhanced the ProvidersPage component to support dynamic addition of OpenAI/Anthropic compatible providers.

open-sse/executors/ollama-local.js

@@ -0,0 +1,14 @@
+import { DefaultExecutor } from "./default.js";
+import { resolveOllamaLocalHost } from "../config/providers.js";
+
+export class OllamaLocalExecutor extends DefaultExecutor {
+  constructor() {
+    super("ollama-local");
+  }
+
+  buildUrl(model, stream, urlIndex = 0, credentials = null) {
+    return `${resolveOllamaLocalHost(credentials)}/api/chat`;
+  }
+}
+
+export default OllamaLocalExecutor;