feat: management api key commands

[Davidonium]

Introduces a new top-level access command group for managing cloud-level authentication to Qdrant Cloud. The feature fills a gap where users could manage cluster-level API keys but had no CLI surface for managing the keys used to authenticate against the Qdrant Cloud API itself.

The access key subcommands support listing, creating, and deleting management keys for an account. On creation, the full key value is returned once and surfaced to the user, with guidance to store it securely since it cannot be retrieved again.

Samples:

$ qcloud access key list
ID                                    CREATED AT
3f7a1b2c-...                          2026-04-01 10:23:00
9e4d8f0a-...                          2026-03-15 08:45:12

$ qcloud access key create
Key ID:    3f7a1b2c-4d5e-6f7a-8b9c-0d1e2f3a4b5c
Key Value: qk_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Store this value securely — it will not be shown again.

$ qcloud access key create --json
{
  "id": "3f7a1b2c-4d5e-6f7a-8b9c-0d1e2f3a4b5c",
  "key": "qk_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "account_id": "a1b2c3d4-..."
}

$ qcloud access key delete 3f7a1b2c-4d5e-6f7a-8b9c-0d1e2f3a4b5c
Management key deleted.

Potential other subcommands under access:

• access user — list and manage account members (invite, remove, update roles)
• access role — manage custom roles and their permissions within the account
• access permission list — list available permissions