Show live server statistics on the server Overview: TPS, players, and operators

The server Overview shows the run state and address but no live statistics. Add widgets for tick rate (TPS) over time, the players currently online with their names, and the operator list.

Scope:

• Read what the server reports about itself while it runs (for example the console list and tps output, or the query protocol where enabled). The widgets show nothing, with a one-line explanation, for a server that does not report a value or is stopped.
• Operators come from ops.json, editable through the existing server commands, never by rewriting the file while the server runs.
• Values are untrusted input from the server process and are bounded before they reach the UI.