feat: implement multi-server support and sync tools

- Introduced ServerRegistry to manage multiple NPM instances
- Added support for NPM_SERVERS JSON environment variable
- Updated all tools to support optional 'server' targeting
- Implemented clone_proxy_host, sync_access_lists, and sync_certificates tools
- Transitioned get_proxy_host_logs to API-based retrieval with local fallback
- Added comprehensive test suite for multi-server management and sync operations

Co-authored-by: claw-io <agent@ben.io>

tests/test_registry.py

@@ -0,0 +1,97 @@
+"""Tests for ServerRegistry."""
+
+import pytest
+
+from npm_mcp.config import settings
+from npm_mcp.server import ServerRegistry
+
+
+def test_registry_fallback_to_single_server(monkeypatch):
+    """Test that registry falls back to single-server settings when empty."""
+    monkeypatch.setattr(settings, "api_url", "http://test-url:81/api")
+    monkeypatch.setattr(settings, "identity", "test-user")
+    monkeypatch.setattr(settings, "secret", "test-pass")
+
+    registry = ServerRegistry(configs=[], default=None)
+
+    assert registry.list_names() == ["default"]
+    assert registry.get_default() == "default"
+
+    client = registry.get()
+    assert client.base_url == "http://test-url:81/api"
+    assert client._identity == "test-user"
+
+
+def test_registry_multiple_servers():
+    """Test that multiple servers are correctly registered."""
+    configs = [
+        {"name": "prod", "url": "http://prod:81/api", "identity": "p", "secret": "ps"},
+        {"name": "dev", "url": "http://dev:81/api", "identity": "d", "secret": "ds"},
+    ]
+
+    registry = ServerRegistry(configs=configs, default="prod")
+
+    assert set(registry.list_names()) == {"prod", "dev"}
+    assert registry.get_default() == "prod"
+
+    prod_client = registry.get("prod")
+    assert prod_client.base_url == "http://prod:81/api"
+
+    dev_client = registry.get("dev")
+    assert dev_client.base_url == "http://dev:81/api"
+
+
+def test_registry_get_default_fallback():
+    """Test that get() falls back to default server when name is None/empty."""
+    configs = [
+        {"name": "prod", "url": "http://prod:81/api", "identity": "p", "secret": "ps"},
+        {"name": "dev", "url": "http://dev:81/api", "identity": "d", "secret": "ds"},
+    ]
+
+    registry = ServerRegistry(configs=configs, default="dev")
+
+    # Name is None
+    client = registry.get(None)
+    assert client.base_url == "http://dev:81/api"
+
+    # Name is empty string
+    client_empty = registry.get("")
+    assert client_empty.base_url == "http://dev:81/api"
+
+
+def test_registry_single_client_no_default_specified():
+    """Test that get() succeeds if there is only 1 server, even if no default is specified."""
+    configs = [
+        {"name": "only-one", "url": "http://only:81/api", "identity": "o", "secret": "os"}
+    ]
+
+    registry = ServerRegistry(configs=configs, default=None)
+
+    assert registry.get_default() is None
+    client = registry.get()
+    assert client.base_url == "http://only:81/api"
+
+
+def test_registry_multiple_clients_no_default_raises():
+    """Test that get() raises KeyError if multiple servers are defined but no default is set."""
+    configs = [
+        {"name": "prod", "url": "http://prod:81/api", "identity": "p", "secret": "ps"},
+        {"name": "dev", "url": "http://dev:81/api", "identity": "d", "secret": "ds"},
+    ]
+
+    registry = ServerRegistry(configs=configs, default=None)
+
+    with pytest.raises(KeyError, match="Multiple servers configured but no default server"):
+        registry.get()
+
+
+def test_registry_invalid_name_raises():
+    """Test that get() raises KeyError for non-existent server names."""
+    configs = [
+        {"name": "prod", "url": "http://prod:81/api", "identity": "p", "secret": "ps"},
+    ]
+
+    registry = ServerRegistry(configs=configs, default="prod")
+
+    with pytest.raises(KeyError, match="Server 'non-existent' not found"):
+        registry.get("non-existent")