feat(library): replace/upgrade an owned album on demand

Add Request.force (migration add_request_force): the pipeline's intake now
skips the "already in library" dedupe for a forced job, so an owned album is
re-downloaded. The import step still keeps the new copy only when it's higher
quality, so a forced upgrade can never downgrade what's on disk.

- Worker: _is_force_job → dedupe bypassed when Request.force.
- POST /api/library/[id]/upgrade finds the matching MonitoredRelease and
  enqueues a force request (guards against stacking on an in-flight job).
- Library route exposes monitoredReleaseId; the album modal shows a
  "Replace / upgrade" button when a release exists.

Worker + web tests added (pipeline force re-acquire; upgrade route).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/library/library-client.tsx

@@ -19,6 +19,7 @@ type Album = {
   year: string | null;
   primaryType: string | null;
   artistMbid: string | null;
+  monitoredReleaseId: string | null;
   trackNames: string[];
 };
 
@@ -115,6 +116,18 @@ export function LibraryClient() {
     refresh();
   }, []);
 
+  async function upgrade() {
+    if (!open) return;
+    const res = await fetch(`/api/library/${open.id}/upgrade`, { method: "POST" }).catch(() => null);
+    if (res && (res.status === 202 || res.ok)) {
+      const body = await res.json().catch(() => null);
+      toast(body?.enqueued === false ? `Already searching for ${open.album}` : `Re-acquiring ${open.album} — keeps it only if better`);
+      show(null);
+    } else {
+      toast((res && (await res.json().catch(() => null))?.error) || "Couldn't start the upgrade");
+    }
+  }
+
   async function checkIntegrity() {
     setChecking(true);
     try {
@@ -349,6 +362,11 @@ export function LibraryClient() {
               </>
             ) : (
               <>
+                {open.monitoredReleaseId ? (
+                  <button className="btn sm ghost" onClick={upgrade}>
+                    Replace / upgrade
+                  </button>
+                ) : null}
                 <button className="btn sm ghost" onClick={startEdit}>
                   Edit metadata
                 </button>