feat(audit): 1.1 — project scaffold, schema types, collector stub, updater trust

- go.mod: module bee/audit
- schema/hardware.go: HardwareIngestRequest types (compatible with core)
- collector/collector.go: Run() stub, logs start/finish, returns empty snapshot
- updater/trust.go: Ed25519 multi-key verification via ldflags injection
- updater/trust_test.go: valid sig, tampered, multi-key any-match, dev build
- cmd/audit/main.go: --output stdout|file:<path>|usb, --version flag
- Version = "dev" by default, injected via ldflags at release

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/updater/trust.go

@@ -0,0 +1,59 @@
+// Package updater handles binary self-update with Ed25519 signature verification.
+// See bible/rules/patterns/release-signing/contract.md for the full contract.
+package updater
+
+import (
+	"crypto/ed25519"
+	"encoding/base64"
+	"fmt"
+	"strings"
+)
+
+// trustedKeysRaw is injected at release build time via:
+//
+//	-ldflags "-X bee/audit/internal/updater.trustedKeysRaw=base64key1:base64key2"
+//
+// Empty in dev builds — updates are disabled when empty.
+var trustedKeysRaw string
+
+// TrustedKeys decodes the embedded public keys.
+// Returns an error if the binary was built without key injection (dev build).
+func TrustedKeys() ([]ed25519.PublicKey, error) {
+	if strings.TrimSpace(trustedKeysRaw) == "" {
+		return nil, fmt.Errorf("dev build: trusted keys not embedded, updates disabled")
+	}
+	var keys []ed25519.PublicKey
+	for _, enc := range strings.Split(trustedKeysRaw, ":") {
+		enc = strings.TrimSpace(enc)
+		if enc == "" {
+			continue
+		}
+		b, err := base64.StdEncoding.DecodeString(enc)
+		if err != nil {
+			return nil, fmt.Errorf("decode trusted key: %w", err)
+		}
+		if len(b) != ed25519.PublicKeySize {
+			return nil, fmt.Errorf("trusted key has wrong size: got %d, want %d", len(b), ed25519.PublicKeySize)
+		}
+		keys = append(keys, ed25519.PublicKey(b))
+	}
+	if len(keys) == 0 {
+		return nil, fmt.Errorf("no valid trusted keys found in build")
+	}
+	return keys, nil
+}
+
+// VerifySignature returns nil if sig was produced by any trusted key over data.
+// Returns an error (never panics) on any failure — caller logs and continues.
+func VerifySignature(data, sig []byte) error {
+	keys, err := TrustedKeys()
+	if err != nil {
+		return err
+	}
+	for _, key := range keys {
+		if ed25519.Verify(key, data, sig) {
+			return nil
+		}
+	}
+	return fmt.Errorf("signature verification failed: no trusted key matched")
+}