Certificates for other hosts: jarl cert get

jarld obtains and renews a certificate for another host; the host asks
for it with one command, waits, downloads it when it is newer than its
copy and runs a hook with the paths in JARL_CERT_* variables.

- Certificates have an owner user; another user can't take the name.
  An existing one is obtained again only when a name is added or
  removed. A new certificates grant (names=) says which names a user
  may have; it is never part of "*". Users may own
  certificates.max_per_user certificates (10) or their own cert_limit.
- POST /certificates/{name}/request; owners may list, show, export and
  delete theirs; keys only over HTTPS, the socket or loopback; every
  download is recorded and shown as "Pulled by".
- CLI: jarl cert get (saved settings, all saved when no name), cert
  saved, cert forget, cert schedule (daily systemd timer, Linux, root).
- Migration 14. Tests: server, auth, and e2e against Pebble.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/static/assets/pages/certificates.js

@@ -35,6 +35,7 @@ export async function render(el) {
       c.uses.includes("web") ? [badge(c.serving ? "web UI (serving)" : "web UI", c.serving ? "ok" : ""), " "] : null,
       c.uses.includes("dns") ? namedUse(c) : null,
       !c.uses.length ? h("span", { class: "muted", title: "Export it to use it in another program" }, "not used by Jarl") : null] },
+    { label: "Owner", render: (c) => c.owner ? h("span", null, c.owner, pulledBy(c)) : h("span", { class: "muted" }, "Jarl") },
     { label: "Source", render: (c) => c.source === "acme" ? h("span", null, "Jarl", h("div", { class: "small muted" }, "challenge " + c.challenge)) : h("span", null, "your files", h("div", { class: "small muted mono" }, c.cert_file)) },
     { label: "Expires", render: (c) => c.not_after ? h("span", null, time(c.not_after), c.source === "acme" && c.next_attempt ? h("div", { class: "small muted" }, "renews " + fmtTime(c.next_attempt)) : null) : h("span", { class: "muted" }, "–") },
     { label: "Status", render: (c) => {
@@ -64,6 +65,15 @@ export async function render(el) {
   }
 }
 
+// pulledBy says who downloaded a certificate for another host, and
+// whether they have the current one.
+function pulledBy(c) {
+  const ps = c.pulled_by || [];
+  if (!ps.length) return h("div", { class: "small muted" }, "not downloaded yet");
+  return ps.map((p) => h("div", { class: "small " + (p.serial === c.serial ? "muted" : "warn-text"), title: p.who + " from " + (p.ip || "?") + ", " + fmtTime(p.at) },
+    p.who.replace(/^token /, "") + ", " + fmtTime(p.at) + (p.serial === c.serial ? "" : " (old: not fetched since the renewal)")));
+}
+
 // namedUse is what named uses a certificate for: DoT and DoH, with the
 // addresses in the tooltip (the details list them).
 function namedUse(c) {