feat: download lifecycle — stalled and failed downloads are given up and searched again; imported ones seed, then go (M502 #5523)

Ported from Fabled Librarian's System 104. A new lifecycle poller, every
ten minutes:
- a download the client fails is given up at once;
- one nobody shares, or still fetching its file list, past the stall
  setting (6 h) is asked for again three times, then given up;
- giving up removes the download with its files, holds the release back
  for a week (release_blocks.expires_at), ends the grab and searches the
  album again, with no limit per album;
- a running download the client stops listing for half an hour ends and is
  searched again, not held back; an empty list is not taken as gone;
- an imported download seeds to ratio 2.0 or 14 days, then is removed;
- a download the client would not remove is asked again every pass.

Every condition and act is one open row per (client, download, condition)
in download_interventions. Activity shows what is wrong with a download and
how often it was retried, why one ended, its seeding, and a banner for a
client that does not answer. A running download can be given up by hand
(set aside for good). The seed ratio, seed days and stall hours are on the
search settings card. The download client lookup moves to
acquire.DownloadClientFor, shared by the importer and the lifecycle.

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

web/src/lib/components/SearchSettingsCard.svelte

@@ -11,13 +11,23 @@
   // for, whether the best release is taken without asking, and which
   // qualities are taken at all. The schedule wakes every ten minutes and
   // keeps to each indexer's searches-per-hour. A finished download is
-  // checked and filed into one of the library's folders (#5522).
+  // checked and filed into one of the library's folders (#5522); it then
+  // seeds until the ratio or the days below, and a download nobody shares
+  // is given up after the hours below (#5523).
 
   const client = useQueryClient();
   const store = createSearchSettingsQuery();
   const query = $derived($store);
 
-  type Form = { auto_grab: boolean; search_interval_hours: number; allowed: string[]; import_root: string };
+  type Form = {
+    auto_grab: boolean;
+    search_interval_hours: number;
+    allowed: string[];
+    import_root: string;
+    seed_ratio: number;
+    seed_days: number;
+    stall_hours: number;
+  };
 
   // The form is the server's settings until edited; saved holds what a save
   // returned until the query catches up.
@@ -32,7 +42,10 @@
       auto_grab: s.auto_grab,
       search_interval_hours: s.search_interval_hours,
       allowed: [...s.allowed_qualities],
-      import_root: s.import_root
+      import_root: s.import_root,
+      seed_ratio: s.seed_ratio,
+      seed_days: s.seed_days,
+      stall_hours: s.stall_hours
     };
   }
 
@@ -55,7 +68,10 @@
         auto_grab: form.auto_grab,
         search_interval_hours: Number(form.search_interval_hours),
         allowed_qualities: form.allowed,
-        import_root: form.import_root
+        import_root: form.import_root,
+        seed_ratio: Number(form.seed_ratio),
+        seed_days: Number(form.seed_days),
+        stall_hours: Number(form.stall_hours)
       });
       edited = null;
       await client.invalidateQueries({ queryKey: qk.searchSettings() });
@@ -158,7 +174,7 @@
         <span class="text-sm text-text-primary">File new music into</span>
         <span class="block text-xs text-text-secondary">
           A download that checks out is copied here as Artist/Album (Year)/Artist - Album - NN -
-          Title, tagged with its MusicBrainz ids. The download itself keeps seeding.
+          Title, tagged with its MusicBrainz ids.
         </span>
         <select
           value={form.import_root || query.data.scan_paths[0]}
@@ -174,11 +190,68 @@
     {:else if query.data.scan_paths.length === 1}
       <p class="text-xs text-text-secondary">
         A download that checks out is copied into <span class="font-mono">{query.data.scan_paths[0]}</span>
-        as Artist/Album (Year)/Artist - Album - NN - Title, tagged with its MusicBrainz ids. The
-        download itself keeps seeding.
+        as Artist/Album (Year)/Artist - Album - NN - Title, tagged with its MusicBrainz ids.
       </p>
     {/if}
 
+    <fieldset class="space-y-3">
+      <legend class="text-sm text-text-primary">After the download</legend>
+      <label class="block">
+        <span class="block text-xs text-text-secondary">
+          The files are copied into the library, so the download goes on sharing until either limit,
+          then is removed with its files. A ratio of 0 removes it once imported; 0 days is no time
+          limit.
+        </span>
+        <span class="mt-1 flex flex-wrap items-center gap-2 text-sm text-text-secondary">
+          Seed to a ratio of
+          <input
+            type="number"
+            min="0"
+            max="100"
+            step="0.1"
+            aria-label="Seed ratio"
+            value={form.seed_ratio}
+            oninput={(e) => edit({ seed_ratio: Number(e.currentTarget.value) })}
+            class="w-20 rounded border border-border bg-background px-2 py-1 text-sm text-text-primary
+                 focus-visible:outline-solid focus-visible:outline-2 focus-visible:outline-accent"
+          />
+          or for
+          <input
+            type="number"
+            min="0"
+            max="365"
+            aria-label="Seed days"
+            value={form.seed_days}
+            oninput={(e) => edit({ seed_days: Number(e.currentTarget.value) })}
+            class="w-20 rounded border border-border bg-background px-2 py-1 text-sm text-text-primary
+                 focus-visible:outline-solid focus-visible:outline-2 focus-visible:outline-accent"
+          />
+          days
+        </span>
+      </label>
+      <label class="block">
+        <span class="block text-xs text-text-secondary">
+          A download nobody is sharing is asked for again three times, ten minutes apart, then given
+          up: removed, held back for a week, and the album searched for again. 0 never gives up for
+          that; a download the client fails is always given up.
+        </span>
+        <span class="mt-1 flex flex-wrap items-center gap-2 text-sm text-text-secondary">
+          Give up on a stalled download after
+          <input
+            type="number"
+            min="0"
+            max="720"
+            aria-label="Stall hours"
+            value={form.stall_hours}
+            oninput={(e) => edit({ stall_hours: Number(e.currentTarget.value) })}
+            class="w-20 rounded border border-border bg-background px-2 py-1 text-sm text-text-primary
+                 focus-visible:outline-solid focus-visible:outline-2 focus-visible:outline-accent"
+          />
+          hours
+        </span>
+      </label>
+    </fieldset>
+
     <p class="text-xs text-text-secondary" data-testid="last-pass">{lastPass(query.data)}</p>
 
     <div class="flex justify-end">