Add lstk setup azure for registering custom cloud

[carole-lavillonniere]

Motivation

Bring the azlocal start-interception flow into lstk so users can register and activate the LocalStack custom cloud in the Azure CLI without a separate Python tool.

Changes

• New lstk setup azure subcommand that registers (or updates) the LocalStack cloud in az, activates it, disables instance discovery, and logs in with dummy service-principal credentials.
• internal/azurecli thin wrapper around the az binary with OTel spans.
• internal/azureconfig owns the cloud-setup flow: health probe of the emulator, cloud-config JSON (mirrors azlocal's trailing-slash convention), and the four az invocations. Emits progress events between steps so the TUI shows what's happening.
• internal/ui/run_azureconfig.go resolves host:port from the Azure container in config.toml, builds the https://azure.<host>:<port> endpoint, and runs the setup under the TUI.
• Fails early with clear messages when there's no Azure container in config, the emulator isn't reachable, az isn't on PATH, or the user isn't in an interactive terminal.

Tests

• Unit tests for BuildEndpoint, cloud-config JSON shape (trailing slashes on management/microsoftGraphResourceId/resourceManager, bare on the AD/log endpoints), and IsRunning against an httptest server.
• Integration tests for the non-interactive error and the missing-Azure-container error.
• Manual: happy path against localstack/localstack-azure-alpha — setup azure then az group list hits LocalStack:

az cloud show --query "{name:name,mgmt:endpoints.resourceManager}"
{
  "mgmt": "https://azure.localhost.localstack.cloud:4566/",
  "name": "LocalStack"
}

Todo

• Wire Azure into knownImages / emulatorHealthPaths / ContainerPort so lstk start can launch the Azure emulator (separate ticket).
• lstk azure proxy passthrough (separate ticket).
• Undo flow (stop-interception equivalent) (separate ticket).

Towards FLC-656