feat(cursor): Integrate Cursor IDE support with OAuth import token flow

- Add CursorExecutor for handling requests to the Cursor API using protobuf over HTTP/2.
- Implement CursorAuthModal for user token import from local SQLite database.
- Update provider models and constants to include Cursor as a supported provider.
- Enhance API service with token validation and user info extraction from Cursor tokens.
- Introduce utility functions for checksum generation and protobuf encoding/decoding for Cursor API interactions.

open-sse/services/model.js

@@ -8,11 +8,13 @@ const ALIAS_TO_PROVIDER_ID = {
   ag: "antigravity",
   gh: "github",
   kr: "kiro",
+  cu: "cursor",
   // API Key providers (alias = id)
   openai: "openai",
   anthropic: "anthropic",
   gemini: "gemini",
   openrouter: "openrouter",
+  cursor: "cursor",
 };
 
 /**