docs: document dashboard-issued iams_live API keys

[Si40Code]

What changed

• document Dashboard self-service API key creation and management
• identify production Developer API keys as iams_live_
• clarify that SDKs send the complete key directly as a Bearer credential, with no client-side token exchange
• replace obsolete calle_test_key placeholders in Authentication and Quickstart
• add the August 11 authentication update to What's New

Why

The public guides still described a separate CALL-E-provisioned Developer API credential. Production uses the Dashboard-issued IAMS AccessKey directly, so the old wording caused developers to request or construct unsupported calle_live_ / calle_test_ credentials.

Impact

Developers can copy the complete Dashboard-issued key into CALLE_API_KEY and use the existing TypeScript or Python SDK configuration unchanged. The HTTP and OpenAPI contract remains standard Bearer authentication.

Production verification

A production probe on August 11, 2026 confirmed that an iams_live_-shaped credential reaches IAMS validation while a calle_live_-shaped credential is rejected by the prefix gate.

Validation

• pnpm run validate
• TypeScript typecheck and static build passed
• 11 OSS deployment tests passed
• 16 Playwright documentation tests passed
• git diff --check passed