refactor(charts): unify on Chart.js, remove Chartist

The admin page was the only consumer of Chartist while the dashboard and
expense report already use Chart.js. Convert the admin "Growth in clients"
(bar) and "Changes by hour" (line) charts to Chart.js using the same
Alpine x-data/x-init canvas pattern as the dashboard, and drop the global
Chartist CSS/JS includes from the base page.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/clj/auto_ap/ssr/ui.clj

@@ -23,8 +23,6 @@
      [:title (str "Integreat | " page-name)]
      [:link {:href "/css/font.min.css", :rel "stylesheet"}]
      [:link {:rel "icon" :type "image/png" :href "/favicon.png"}]
-     [:link {:rel "stylesheet" :href "//cdn.jsdelivr.net/chartist.js/latest/chartist.min.css"}]
-     [:script {:src "//cdn.jsdelivr.net/chartist.js/latest/chartist.min.js"}]
      [:link {:rel "stylesheet", :href "/output.css"}]
      [:script {:src "https://cdn.plaid.com/link/v2/stable/link-initialize.js"}]
      [:script {:src "https://cdn.jsdelivr.net/npm/@ryangjchandler/alpine-tooltip@1.x.x/dist/cdn.min.js" :defer true}]