M6: version history — note revisions + restore

A note's title+body is snapshotted on each edit that changes either, so an accidental overwrite can be viewed and restored (task 1906). Underwrites 'dump freely, nothing is lost'.

Backend: note_revisions table (migration 0014) + NoteRevision model; update_note records a revision of the PRE-edit state whenever title/body changes; GET /api/notes/<id>/revisions (newest 50) and POST /api/notes/<id>/revisions/<rev_id>/restore (snapshots the current state first so restore is itself undoable, then applies the revision with the usual title/body ripple — display name, links, #tags, backlinks). Title+body only in v1.

Frontend: a History toggle in the modal editor opens a panel of past versions (timestamp + preview) with per-row Restore. Store gains fetchRevisions/restoreRevision.

Migration 0014 runs on deploy; DB behavior operator-verified (no Postgres CI lane).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/NoteEditor.vue

@@ -8,7 +8,7 @@ import Icon from "./Icon.vue";
 import LabelPicker from "./LabelPicker.vue";
 import NoteChecklist from "./NoteChecklist.vue";
 import { fromLocalInput, toLocalInput } from "../notes/datetime";
-import type { Note, NoteLabel } from "../stores/notes";
+import type { Note, NoteLabel, NoteRevision } from "../stores/notes";
 import { LABEL_CHIP_CLASSES, type NoteColor } from "../notes/colors";
 
 // One editor for BOTH composing and editing. `inline` renders the board composer
@@ -457,6 +457,47 @@ async function act(fn: () => Promise<void>) {
   emit("close");
 }
 
+// ---- version history (modal edit only) ----
+const showHistory = ref(false);
+const revisions = ref<NoteRevision[]>([]);
+
+async function loadRevisions() {
+  if (!noteId.value) {
+    revisions.value = [];
+    return;
+  }
+  try {
+    revisions.value = await notes.fetchRevisions(noteId.value);
+  } catch {
+    revisions.value = [];
+  }
+}
+function toggleHistory() {
+  showHistory.value = !showHistory.value;
+  if (showHistory.value) void loadRevisions();
+}
+async function restoreRevisionAt(revId: string) {
+  const id = noteId.value;
+  if (!id) return;
+  const updated = await notes.restoreRevision(id, revId);
+  title.value = updated.title ?? "";
+  body.value = updated.body;
+  color.value = updated.color;
+  baseline.value = { title: updated.title, body: updated.body, color: updated.color };
+  void loadRevisions(); // the pre-restore state became a new revision
+}
+function revLabel(iso: string | null): string {
+  if (!iso) return "";
+  return new Date(iso).toLocaleString(undefined, { month: "short", day: "numeric", hour: "numeric", minute: "2-digit" });
+}
+function revPreview(rev: NoteRevision): string {
+  const t = (rev.title ?? "").trim();
+  const b = rev.body.trim().replace(/\s+/g, " ");
+  const s = t && b ? `${t} — ${b}` : t || b;
+  if (!s) return "(empty)";
+  return s.length > 80 ? `${s.slice(0, 80)}…` : s;
+}
+
 defineExpose({ open });
 </script>
 
@@ -637,6 +678,29 @@ defineExpose({ open });
             </div>
           </div>
         </div>
+
+        <div
+          v-if="!inline && !isCreate && showHistory"
+          class="flex flex-col gap-1 border-t border-neutral-100 pt-2 dark:border-neutral-800"
+        >
+          <p class="text-xs font-semibold uppercase tracking-wide text-neutral-400">History</p>
+          <p v-if="!revisions.length" class="text-xs text-neutral-400">
+            No earlier versions yet — your edits will show up here.
+          </p>
+          <ul v-else class="flex max-h-40 flex-col gap-0.5 overflow-y-auto">
+            <li v-for="rev in revisions" :key="rev.id" class="flex items-center gap-2 rounded-md px-1 py-1 text-xs">
+              <span class="shrink-0 tabular-nums text-neutral-400">{{ revLabel(rev.created_at) }}</span>
+              <span class="min-w-0 flex-1 truncate text-neutral-600 dark:text-neutral-300">{{ revPreview(rev) }}</span>
+              <button
+                type="button"
+                class="shrink-0 rounded px-1.5 py-0.5 font-medium text-brand-700 hover:bg-brand/10 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:text-brand"
+                @click="restoreRevisionAt(rev.id)"
+              >
+                Restore
+              </button>
+            </li>
+          </ul>
+        </div>
       </div>
 
       <div class="flex items-center justify-between gap-2 border-t border-neutral-100 px-3 py-2 dark:border-neutral-800">
@@ -675,6 +739,18 @@ defineExpose({ open });
             :model-value="labelList"
             @update:model-value="onLabelsChange"
           />
+          <button
+            v-if="!inline && !isCreate"
+            type="button"
+            class="icon-btn"
+            :class="showHistory ? 'text-brand-700 dark:text-brand' : ''"
+            title="Version history"
+            aria-label="Version history"
+            :aria-pressed="showHistory"
+            @click="toggleHistory"
+          >
+            <Icon name="history" />
+          </button>
           <template v-if="!inline && !isCreate && !liveNote.trashed">
             <button
               type="button"