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.

src/lib/oauth/providers.js

@@ -13,6 +13,7 @@ import {
   ANTIGRAVITY_CONFIG,
   GITHUB_CONFIG,
   KIRO_CONFIG,
+  CURSOR_CONFIG,
 } from "./constants/oauth";
 
 // Provider configurations
@@ -656,6 +657,22 @@ const PROVIDERS = {
       },
     }),
   },
+
+  cursor: {
+    config: CURSOR_CONFIG,
+    flowType: "import_token",
+    // Cursor uses import token flow - tokens are extracted from local SQLite database
+    // No OAuth flow needed, handled by /api/oauth/cursor/import route
+    mapTokens: (tokens) => ({
+      accessToken: tokens.accessToken,
+      refreshToken: null, // Cursor doesn't have public refresh endpoint
+      expiresIn: tokens.expiresIn || 86400,
+      providerSpecificData: {
+        machineId: tokens.machineId,
+        authMethod: "imported",
+      },
+    }),
+  },
 };
 
 /**