Free unused attachments, and keep versions by count rather than by age

Two rules governed version retention: the newest 50 per note, and a sweep
of anything past 90 days. The second was wrong. The count already bounds
what a note can accumulate, so age only ever deleted history nothing had
replaced — and it bit hardest exactly where history is most wanted, a
note left alone for a quarter of a year losing its whole past for having
done nothing. It is off unless VERSION_RETENTION_DAYS is set.

How many versions to keep is now a notebook's own setting, falling back
to the server default when left empty. A reference notebook can keep
fifty of everything while a scratch one keeps three.

That makes freeing attachments answerable. A picture taken out of a note
cannot be deleted straight away: the versions from before still show it,
and restoring one would find a hole. It is released once no current note
and no kept version refers to it — which, with retention by count, is
when the last version holding it is pushed out.

The server cannot look for itself, bodies being encrypted, so the client
reports a note's attachments on every save as it already does for links,
and a version inherits what the note held when it was snapshotted — by
definition what that version contains.

Two things make it safe rather than merely plausible. Silence is not
"uses nothing": a note written before this existed has no rows, which
looks identical to one with no pictures, so nothing is released for a
user while any of their notes has yet to report — the prefetch that fills
the search index reports for them on its first pass. And an upload has a
row before the note using it does, so recent attachments are left alone.

POST /api/admin/housekeeping runs the sweep on demand.

Caught while testing: the same block of markup had been pasted into the
create-notebook dialog as well, where the state it referenced did not
exist — the dialog crashed on open.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/ui/NotebookModals.jsx

@@ -4,6 +4,15 @@ import { COVERS } from "./constants.jsx";
 export function EditNotebookModal({ notebook, onClose, onSave, dark }) {
   const [name, setName] = useState(notebook.name);
   const [sel, setSel] = useState(notebook.cover);
+  // Empty means "use the server's default", which is why it is a string here and
+  // not a number with a stand-in value.
+  const [versions, setVersions] = useState(notebook.maxVersions == null ? "" : String(notebook.maxVersions));
+
+  const save = () => {
+    if (!name.trim()) return;
+    const n = versions.trim() === "" ? null : Math.max(1, Math.round(Number(versions)));
+    onSave({ name: name.trim(), cover: sel, maxVersions: Number.isFinite(n) ? n : null });
+  };
   const T = useMemo(
     () => ({
       bg: dark ? "#161b22" : "#fff",
@@ -69,9 +78,40 @@ export function EditNotebookModal({ notebook, onClose, onSave, dark }) {
             boxSizing: "border-box",
           }}
           onKeyDown={(e) => {
-            if (e.key === "Enter" && name.trim()) onSave({ name: name.trim(), cover: sel });
+            if (e.key === "Enter") save();
           }}
         />
+        <div style={{ marginBottom: 18 }}>
+          <label style={{ fontSize: 12, color: T.muted, display: "block", marginBottom: 5 }}>
+            Versionen pro Notiz
+          </label>
+          <input
+            type="number"
+            min="1"
+            value={versions}
+            onChange={(e) => setVersions(e.target.value)}
+            placeholder="Vorgabe"
+            aria-label="Versions per note"
+            style={{
+              width: 110,
+              padding: "8px 12px",
+              borderRadius: 10,
+              border: `1px solid ${T.border}`,
+              background: dark ? "#0d1117" : "#f6f8fa",
+              color: T.text,
+              fontSize: 14,
+              outline: "none",
+              boxSizing: "border-box",
+            }}
+            onKeyDown={(e) => {
+              if (e.key === "Enter") save();
+            }}
+          />
+          <div style={{ fontSize: 11, color: T.muted, marginTop: 6, lineHeight: 1.5 }}>
+            Ältere Fassungen werden erst gelöscht, wenn neue sie verdrängen — nicht nach Zeit. Leer lassen für
+            die Vorgabe des Servers.
+          </div>
+        </div>
         <div style={{ marginBottom: 22 }}>
           <div style={{ fontSize: 12, color: T.muted, marginBottom: 8 }}>Cover style</div>
           <div style={{ display: "grid", gridTemplateColumns: "repeat(5,1fr)", gap: 8 }}>
@@ -115,7 +155,7 @@ export function EditNotebookModal({ notebook, onClose, onSave, dark }) {
           </button>
           <button
             onClick={() => {
-              if (name.trim()) onSave({ name: name.trim(), cover: sel });
+              save();
             }}
             style={{
               padding: "8px 20px",