oauth-client-browser: accept DIDs when preparing login

[Kzoeps]

Summary

HappyViewBrowserClient.prepareLogin() cannot start OAuth login from a DID.

The method accepts a handle and always passes it to the handle resolver:

https://github.com/gamesgamesgamesgamesgames/happyview/blob/cbed465e5301d59685eea4ad917a599f82e6e92c/packages/oauth-client-browser/src/browser-client.ts#L122-L131

const resolvedDid = await this.handleResolver.resolve(handle)

Passing an identifier such as did:plc:abc therefore attempts handle resolution and fails, even though the client already has a DID resolver for the next step.

Expected behavior

prepareLogin, login, signIn, signInRedirect, and signInPopup should accept either a handle or DID as the login identifier.

Actual behavior

Only handles work. A DID is incorrectly treated as a handle, preventing OAuth login from starting.