feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

internal/webapp/templates/notifications.html

@@ -0,0 +1,32 @@
+{{define "body"}}<section class="card">
+  <h1>Recent notifications</h1>
+  <p class="muted">Last 50 notifications emitted by this worker (Phase 1: selfcheck alerts only).</p>
+  <p><button type="button" disabled title="{{.ResendTooltip}}">Resend selected</button>
+     <span class="muted">{{.ResendTooltip}}</span></p>
+  <table>
+    <thead>
+      <tr>
+        <th>Channel</th>
+        <th>Subject</th>
+        <th>Body</th>
+        <th>Status</th>
+        <th>Error</th>
+        <th>When</th>
+      </tr>
+    </thead>
+    <tbody>
+      {{range .Rows}}
+      <tr>
+        <td>{{.Channel}} ({{.Kind}})</td>
+        <td>{{.Subject}}</td>
+        <td><code>{{.Body}}</code></td>
+        <td>{{if .OK}}<span class="ok">delivered</span>{{else}}<span class="error">failed</span>{{end}}</td>
+        <td>{{.Error}}</td>
+        <td>{{fmtTime .At}}</td>
+      </tr>
+      {{else}}
+      <tr><td colspan="6" class="muted">No notifications yet.</td></tr>
+      {{end}}
+    </tbody>
+  </table>
+</section>{{end}}