Remove sponsor token gating

Unlock all locally gated features without a sponsor token. The change sits
in util/sponsor/auth.go instead of the ~68 device constructors:

- Subject defaults to a non-empty value, so RedactedStatus reports an active
  sponsorship and the frontend unlocks isSponsor
- IsAuthorized always returns true, opening every caller including the
  modbus proxy and the optimizer gate
- ConfigureSponsorship still validates a configured token but never fails,
  so an expired token no longer aborts startup

Drops TestAlpitronicSponsorGate and TestSigenergyEVDCSponsorGate, which
asserted exactly the gate that is removed here.

Cloud-backed services (optimizer API, remote access, cloud vehicles,
telemetry) still require a real token - those are checked server side.

See FORK.md.

util/sponsor/auth.go

@@ -35,10 +35,15 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+// unlocked is the sponsorship subject used by this fork. Sponsor gating is
+// removed here, so Subject is never empty and IsAuthorized always holds.
+const unlocked = "unlocked"
+
 var (
-	mu             sync.RWMutex
-	Subject, Token string
-	ExpiresAt      time.Time
+	mu        sync.RWMutex
+	Subject   = unlocked
+	Token     string
+	ExpiresAt time.Time
 )
 
 func machineID() string {
@@ -51,9 +56,8 @@ const unavailable = "sponsorship unavailable"
 const startupTimeout = 30 * time.Second
 
 func IsAuthorized() bool {
-	mu.RLock()
-	defer mu.RUnlock()
-	return len(Subject) > 0
+	// sponsorship gating removed in this fork
+	return true
 }
 
 func IsAuthorizedForApi() bool {
@@ -62,8 +66,29 @@ func IsAuthorizedForApi() bool {
 	return IsAuthorized() && Subject != unavailable && Token != ""
 }
 
-// check and set sponsorship token
+// ConfigureSponsorship validates a sponsor token when one is configured, but
+// never fails: sponsorship is not required in this fork. A valid token is
+// still picked up so cloud-backed services keep working for real sponsors.
 func ConfigureSponsorship(token string) error {
+	err := configureSponsorship(token)
+
+	mu.Lock()
+	defer mu.Unlock()
+
+	if err != nil {
+		// stay unlocked, but do not offer a rejected token to cloud services
+		Token = ""
+	}
+
+	if Subject == "" {
+		Subject = unlocked
+	}
+
+	return nil
+}
+
+// check and set sponsorship token
+func configureSponsorship(token string) error {
 	mu.Lock()
 	defer mu.Unlock()