feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

internal/webapp/templates/checks.html

@@ -0,0 +1,34 @@
+{{define "body"}}<section class="card">
+  <h1>Recent checks</h1>
+  <p class="muted">Last 50 results produced by this worker.</p>
+  <p><button type="button" disabled title="{{.RunNowTooltip}}">Run now</button>
+     <span class="muted">{{.RunNowTooltip}}</span></p>
+  <table>
+    <thead>
+      <tr>
+        <th>Monitor</th>
+        <th>Check</th>
+        <th>Kind</th>
+        <th>Host</th>
+        <th>State</th>
+        <th>Duration (ms)</th>
+        <th>Error</th>
+      </tr>
+    </thead>
+    <tbody>
+      {{range .Rows}}
+      <tr>
+        <td>{{.MonitorID}}</td>
+        <td>{{.CheckID}}</td>
+        <td>{{.Kind}}</td>
+        <td>{{.Host}}</td>
+        <td>{{.State}}</td>
+        <td>{{.DurationMs}}</td>
+        <td>{{.Error}}</td>
+      </tr>
+      {{else}}
+      <tr><td colspan="7" class="muted">No checks yet. Once the main app assigns jobs to this worker, results will appear here.</td></tr>
+      {{end}}
+    </tbody>
+  </table>
+</section>{{end}}