Web dashboard step 6: jobs and stats

Job catalogue and daily-epub job run, the systemd job unit and polkit rule,
SystemdRunner/MockRunner, the Jobs pages with status and journal tail, the
stats_data refactor with a byte-identical CLI, the stats page and the
overview sparklines.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NHyYupFdBiR4VfoUM7NjSM

systemd/50-daily-epub.rules

@@ -0,0 +1,8 @@
+polkit.addRule(function (action, subject) {
+  if (action.id == "org.freedesktop.systemd1.manage-units" &&
+      subject.user == "daily-epub" &&
+      action.lookup("verb") == "start" &&
+      /^daily-epub-job@[a-z0-9-]+\.service$/.test(action.lookup("unit"))) {
+    return polkit.Result.YES;
+  }
+});