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/ssh.go

@@ -327,11 +327,6 @@ func loadProxmoxHostKeys(host string) ([][]byte, error) {
 	return entries, nil
 }
 
-// getPublicKey reads the SSH public key from the default directory
-func (p *Proxy) getPublicKey() (string, error) {
-	return p.getPublicKeyFrom(p.sshKeyPath)
-}
-
 // getPublicKeyFrom reads the SSH public key from a specific directory
 func (p *Proxy) getPublicKeyFrom(keyDir string) (string, error) {
 	pubKeyPath := filepath.Join(keyDir, "id_ed25519.pub")
@@ -527,12 +522,6 @@ func (p *Proxy) pushSSHKeyFrom(nodeHost, keyDir string) error {
 	return nil
 }
 
-// pushSSHKey adds the proxy's public key to a node's authorized_keys with IP restrictions
-// Automatically upgrades old keys without from= restrictions
-func (p *Proxy) pushSSHKey(nodeHost string) error {
-	return p.pushSSHKeyFrom(nodeHost, p.sshKeyPath)
-}
-
 // testSSHConnection verifies SSH connectivity to a node
 func (p *Proxy) testSSHConnection(nodeHost string) error {
 	startTime := time.Now()