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.

docs/web-ui/shape.md

@@ -16,13 +16,10 @@
 - `GET /static/*` → bundled CSS + JS produced by esbuild
   (`frontend/packages/{dashboard,agent}/build.mjs`). Both pages
   pull the shared terminal pane + Catppuccin palette + typography
-  from `@hive/shared` (was `hive-fr0nt`); the dashboard ships one
-  CSS bundle per page (`colors.css` + `theme.css` + `common.css`,
-  loaded by every page, plus a page-specific bundle —
-  `dashboard.css` /
-  `stats.css`);
+  from `@hive/shared` (was `hive-fr0nt`); the dashboard ships
+  `colors.css` + `theme.css` + `common.css` + `dashboard.css`;
   `common.css` inlines `@hive/shared`'s
-  `base.css` + `terminal.css` + `tabs.css` + `chrome.css` +
+  `base.css` + `terminal.css` + `tabs.css` +
   `pill.css` via esbuild's `@import` resolution.
   `terminal.js` exports `{ create, linkify }` as ES module
   members; a back-compat shim in the IIFE bodies still exposes