Add Meta Muse premium provider and Thinking provenance

[witbrock]

Summary

• add Meta Muse muse-spark-1.3 as an actor-scoped premium provider using META_API_KEY and the streaming Responses contract
• keep provider/model eligibility additive and exact, with no implicit fallback
• show Class: premium and bounded credential provenance in the Debug Thinking-card LLM input row
• distinguish exact exchange credentials from turn-wide backup-key use across active, immediate-completed, and retained cards

Validation

• 24 focused Meta/settings/live-projection backend tests
• 75 infrastructure, utility, dotenv, and catalogue tests
• 315 frontend tests covering Meta settings, model preferences, telemetry, and Thinking cards
• JavaScript lint, Python syntax, focused Ruff checks, and git diff checks

External provider status

• authenticated Meta catalogue discovery succeeded for muse-spark-1.3
• the bounded generation probe reached Meta and returned billing_not_configured (HTTP 402); the implementation reports that failure without silently falling back