Add live dashboard with SSE job events

Expose /jobs, /dedup, and /events routes backed by a new EventBus that
broadcasts job lifecycle and per-job progress over SSE. Serve a static
dashboard from front/ that lists pending and in-progress jobs, streams
agent activity, and shows completed reviews.

Also add migrate-apply/migrate-generate scripts that load .env, update
the Containerfile to ship the front assets and use the apply script, and
refresh the roadmap.

front/js/job-card.js

@@ -0,0 +1,61 @@
+// Carte d'un job. Le détail (id, event, date) est replié par défaut ; le
+// bouton « Watch activity » remonte un évènement `job-select` que le dashboard
+// écoute pour ouvrir le flux d'activité du job.
+
+import { escapeHtml, relativeTime } from "./api.js";
+
+class JobCard extends HTMLElement {
+  set job(value) {
+    this._job = value;
+    this.render();
+  }
+
+  get job() {
+    return this._job;
+  }
+
+  set selected(value) {
+    this._selected = Boolean(value);
+    this.render();
+  }
+
+  connectedCallback() {
+    this.render();
+  }
+
+  render() {
+    if (!this._job) return;
+    const job = this._job;
+
+    // Préserve l'état replié/déplié à travers les re-rendus (mises à jour SSE).
+    const open = this._details?.open ? " open" : "";
+
+    this.innerHTML = `
+      <details class="job" data-selected="${this._selected ? "true" : "false"}"${open}>
+        <summary class="job-head">
+          <span class="chev" aria-hidden="true"></span>
+          <span class="job-repo">${escapeHtml(job.repo)}</span>
+          <span class="job-pr">#${job.pr}</span>
+        </summary>
+        <div class="job-info">
+          <dl>
+            <div><dt>Job</dt><dd>${job.id}</dd></div>
+            ${job.event_id != null ? `<div><dt>Event</dt><dd>${job.event_id}</dd></div>` : ""}
+            <div><dt>Created</dt><dd>${escapeHtml(relativeTime(job.created_at))}</dd></div>
+          </dl>
+          <button class="button button-secondary job-watch" type="button">Watch activity</button>
+        </div>
+      </details>`;
+
+    this._details = this.querySelector("details");
+    this.querySelector(".job-watch").addEventListener("click", () => this.select());
+  }
+
+  select() {
+    this.dispatchEvent(
+      new CustomEvent("job-select", { detail: { id: this._job.id }, bubbles: true }),
+    );
+  }
+}
+
+customElements.define("steep-job-card", JobCard);