Use HTMX fragements on the fitness dashboard

assets/fitness/main.html

@@ -1,10 +1,12 @@
+{{/* A chart's controls re-fetch only that chart (fitnessHandler.serveFragment),
+sending every chart's controls so the server can update the page URL. */}}
 {{define "fitnessChart"}}
-<section class="fitness-chart panel">
+<section class="fitness-chart panel" hx-get="./" hx-vals='{"chart": "{{.Param}}"}' hx-trigger="change" hx-include="closest .fitness-dash" hx-target="this" hx-swap="outerHTML" hx-sync="this:replace">
     <div class="fitness-chart-header row space-between">
         <span class="caption">{{.Title}}</span>
         <div class="row fitness-controls">
-            <label class="fitness-absolute"><input type="checkbox" data-fitness-absolute="{{.Param}}-absolute"{{if .Absolute}} checked{{end}}> Absolute</label>
-            <select class="input fitness-range" data-fitness-range="{{.Param}}" aria-label="{{.Title}} time range">
+            <label class="fitness-absolute"><input type="checkbox" name="{{.Param}}-absolute" value="1"{{if .Absolute}} checked{{end}}> Absolute</label>
+            <select class="input fitness-range" name="{{.Param}}" aria-label="{{.Title}} time range">
                 {{range .Options}}<option value="{{.Value}}"{{if .Selected}} selected{{end}}>{{.Label}}</option>{{end}}
             </select>
         </div>