GO-4642: Scoped Auth Tokens

[jmetrikat]

Introduces scoped authentication tokens with three levels of access:

• Limited: Used for WebClipper - AccountSelect (to be deprecated), ObjectSearch, ObjectShow, ObjectCreate, ObjectCreateFromURL, BlockPreview, BlockPaste, and BroadcastPayloadEvent.
• JsonAPI: Restricts access to JSON API only; direct gRPC API calls are not permitted.
• Full: Provides full access, but not available via LocalLink.

RpcAccountLocalLinkNewChallengeRequest now takes Scope model.AccountAuthLocalApiScope to enable scoped key generation through local link challenge.

[github-actions]

New Coverage	50.6% of statements
Patch Coverage	19.5% of changed statements (23/118)

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