Add Open Cosmos integration flow

[DattSpark]

Summary

Adds Open Cosmos account connection support to the Linked Accounts page using the OAuth 2.0 Authorization Code flow with PKCE (Proof Key for Code Exchange).

Changes

• Add Open Cosmos connect and disconnect controls.
• Exchange authorization codes and refresh expired access tokens.
• Send OAuth credentials to workspace-services for per-user, per-workspace storage.
• Keep tokens out of browser persistent storage.
• Restore the selected workspace menu page after the OAuth redirect. (src\components\WorkspaceMenu\WorkspaceMenu.tsx)
• Prevent duplicate authorization-code exchanges in React StrictMode.
• Add the required Open Cosmos environment configuration (new env vars).

Validation

[GeoSpark]

LGTM

[GeoSpark]

Are the Trivy scan failures worth fixing? It seems it just needs some packages updating.

[DattSpark]

Are the Trivy scan failures worth fixing? It seems it just needs some packages updating.

Yes, It's worth resolving them, but I think it should be a separate pull request. One that focuses solely on upgrading those libraries and testing that everything is working correctly afterward.