remove the hive dashboard's stats page and the price table behind it

The ST4TS page (/stats.html), GET /api/stats-hive, hive-c0re's hive_stats
rollup and the modelPrices option that only fed its cost estimate are
gone. Each agent's own /stats page and the turn-stats database it reads
are unchanged. Setting modelPrices now fails evaluation with a message
saying so.

frontend/packages/swarm-ui/test/links-menu.test.mjs

@@ -17,7 +17,7 @@ test("a link the menu was handed opens in a new tab, without a referrer", () =>
 
 test("a page of the same site opens in place", () => {
   assert.deepEqual(
-    linkAttrs({ label: "stats", url: "/stats.html", external: false }),
+    linkAttrs({ label: "api docs", url: "/api/docs/", external: false }),
     {},
   );
 });