feat(gns3-copilot): add get_gns3_server_host utility and integrate into Nornir tools

- Add `get_gns3_server_host()` function to `connector_factory.py` for extracting GNS3 server hostname from controller, config, or default URL
- Export new function in `__init__.py` for public API access
- Replace `os.getenv("GNS3_SERVER_HOST", "127.0.0.1")` calls with `get_gns3_server_host()` in Nornir configuration tools (`config_tools_nornir.py`, `display_tools_nornir.py`)
- Ensures consistent host detection across tools using the same priority logic as `get_gns3_connector`

gns3server/agent/gns3_copilot/gns3_client/__init__.py

@@ -27,7 +27,11 @@ Main functions:
 - get_gns3_connector_with_llm_config: Factory function to create connector AND retrieve LLM config
 """
 
-from .connector_factory import get_gns3_connector, get_gns3_connector_with_llm_config
+from .connector_factory import (
+    get_gns3_connector,
+    get_gns3_connector_with_llm_config,
+    get_gns3_server_host,
+)
 from .custom_gns3fy import (
     CONSOLE_TYPES,
     LINK_TYPES,
@@ -93,6 +97,7 @@ __all__ = [
     "GNS3UpdateDrawingTool",
     "get_gns3_connector",
     "get_gns3_connector_with_llm_config",
+    "get_gns3_server_host",
     "add_file_to_index",
     "get_file_list",
 ]