chore: remove legacy proxy handlers and unused functions

Remove legacy V1 handlers replaced by V2 versions:
- sendError (replaced by sendErrorV2)
- handleGetStatus (replaced by handleGetStatusV2)
- handleEnsureClusterKeys (replaced by handleEnsureClusterKeysV2)
- handleRegisterNodes (replaced by handleRegisterNodesV2)
- handleGetTemperature (replaced by handleGetTemperatureV2)

Also remove related unused functions:
- getPublicKey wrapper (only getPublicKeyFrom is used)
- pushSSHKey wrapper (only pushSSHKeyFrom is used)
- nodeValidator.ipAllowed method (standalone ipAllowed is used)
- validateConfigFile (never called)
- runServiceDebug (Windows debug mode, never called)

cmd/pulse-sensor-proxy/validation.go

@@ -591,21 +591,6 @@ func (v *nodeValidator) getClusterMembers(ctx context.Context) (map[string]struc
 	return result, nil
 }
 
-func (v *nodeValidator) ipAllowed(ip net.IP) bool {
-	if ip == nil {
-		return false
-	}
-	if _, ok := v.allowHosts[ip.String()]; ok {
-		return true
-	}
-	for _, network := range v.allowCIDRs {
-		if network.Contains(ip) {
-			return true
-		}
-	}
-	return false
-}
-
 func ipAllowed(ip net.IP, hosts map[string]struct{}, cidrs []*net.IPNet) bool {
 	if ip == nil {
 		return false