docs: README still describes a FerrFlow-only Go operator, omits FerrVault CRDs, SAT mode, and the Rust CLI

[BryanFRD]

Problem

README.md is significantly out of sync with what the repo now ships:

• Title is # ferrflow-operator and the prose says it "syncs secrets stored in FerrFlow" — the repo is now FerrLabs/FerrVault and the product is FerrVault.
• It documents only the ferrflow.io/v1alpha1 CRDs (FerrFlowConnection, FerrFlowSecret). The ferrvault.com/v1alpha1 CRDs (FerrVaultConnection, FerrVaultSecret) shipped in v2.0.0 (Operator: add ferrvault.io/v1alpha1 CRDs alongside ferrflow.io #93, CHANGELOG) and are registered in cmd/main.go + the Helm chart (charts/ferrflow-operator/templates/crd-ferrvault*.yaml) but appear nowhere in the README.
• No mention of mode=ferrvault / the SAT (sat_…) auth against POST /v1/operator/secrets/reveal (internal/ferrflow/client.go:312 RevealFromVault), even though that is the new product's primary path.
• The repo now also contains a Rust consumer CLI (cli/, its own README.md) and a GitHub Action (action/) — the top-level README never references them.
• Badges point at FerrLabs/FerrFlow-Operator (lines 3-5) which 404s under the renamed repo, while the Scorecard badge (line 6) already uses FerrLabs/FerrVault — inconsistent.
• The "Prerequisites in FerrFlow" section points at FerrLabs/Application and api@v4.0.0 endpoints, not the FerrVault SaaS endpoints the operator now targets.

Why it matters

The README is the entry point for anyone installing the operator. Right now it documents an auth mode and CRD set that are on the way out (#82) and hides the new ones, so a new user following it configures the legacy path.

Proposed approach

Refresh README.md: rename to FerrVault, document both CRD groups during the transition (with a note that ferrflow.io is deprecated pending #82), add the mode: ferrvault + SAT example, link cli/ and action/, fix the badge URLs. Coordinate wording with the rename tracker #82 so this doesn't drift again.

Acceptance criteria

• README reflects the FerrVault brand, both CRD groups, and SAT mode.
• All badge URLs resolve.
• CLI and Action are linked.