chore(oss): audit the server package and resync the SDK mirrors

Split the 657-line operation service into eor, submit, and verify
modules, add the AGENT_REVOKED and KEY_RETIRED codes the Backend already
emits, and condense every multi-line comment. Mirror Node, Python, and
Go at 2.1.0 with the deep-health 503, non-idempotent retry, rotation
grace, and path-encoding fixes. Document which routes and response
fields the self-hosted server does not provide.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

sdks/go/webhooks.go

@@ -0,0 +1,29 @@
+package elydora
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// ListWebhooks retrieves all registered webhooks for the organization.
+func (c *Client) ListWebhooks() (*ListWebhooksResponse, error) {
+	var result ListWebhooksResponse
+	if err := c.doGet("/v1/webhooks", &result); err != nil {
+		return nil, err
+	}
+	return &result, nil
+}
+
+// RegisterWebhook registers a new webhook endpoint for the organization.
+func (c *Client) RegisterWebhook(req *RegisterWebhookRequest) (*RegisterWebhookResponse, error) {
+	var result RegisterWebhookResponse
+	if err := c.doPost("/v1/webhooks", req, &result); err != nil {
+		return nil, err
+	}
+	return &result, nil
+}
+
+// DeleteWebhook deletes a registered webhook by ID.
+func (c *Client) DeleteWebhook(webhookID string) error {
+	return c.doRequest(http.MethodDelete, fmt.Sprintf("/v1/webhooks/%s", webhookID), nil, nil)
+}