The Lark SDK v3's built-in token retry loop does not clear stale tokens
from cache when the server returns error 99991663 (tenant_access_token
invalid), causing all API calls to fail until the token naturally
expires (~2 hours).
- Add tokenCache struct (implementing larkcore.Cache) with
Get/Set/InvalidateAll methods and proper expired-entry cleanup
- Wire custom cache into lark.NewClient via WithTokenCache()
- Add invalidateTokenOnAuthError helper called in all API methods