Vortex Nexus v1.0.0 — first stable release

First stable release of Vortex Nexus, adding governed provider pricing,
durable billing evidence, and optional FIPS cryptography.

Highlights:
- Governed provider-pricing synchronization with validation, reviewable
  plans, quarantine handling, and historical rate cards
- Exact decimal cost calculation with persisted pricing evidence across
  gateway, ingest, analytics, and billing workflows
- Pricing history and cost visibility in the Next.js console and CLI
- Improved provider routing for reasoning models and tool calls
- Optional FIPS cryptographic builds across Nexus runtime services
- Packaged release evidence with SBOM, vulnerability-scan, provenance,
  signature-verification, and report artifacts