desktop: Import and Export work offline; the menu toggle is reachable; errors say why

Export and Import were a link to the server and a reject("needs a server") on the
desktop. Both now run in the core with no server:

- core/src/local/portable.rs builds the same zip the server writes (notes.json,
  a Markdown file per note, each attachment this device holds) and reads either
  export marker or a Google Keep Takeout zip, with the server's decompression
  budget and an all-or-nothing transaction. Export saves to Downloads (no new
  plugin) and the sidebar says where; Import takes the archive as raw IPC bytes.
- core/testdata/portable.json pins the format for both copies: the server runs
  its Keep and native readers against it (test_portable_fixture.py) and checks
  its real export's keys (test_integration.py); the core runs the same cases.
- Found on the way: both importers skipped a Keep note that is only a photo as
  "empty". It now imports, on the server and in the core.
- New dependency, approved: `zip` (deflate only) plus `flate2` on its pure-Rust
  backend, both already in the lockfile.

The AppImage applications-menu toggle moves from Account, which the desktop
never shows, to the Sync page; the first-run prompt now says so.

errorMessage (#5236) replaces the hand-rolled `.error ?? …` / `.message ?? e`
reads at the remaining catch sites, so a desktop failure shows its real reason.

Task #5170.

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

frontend/src/components/AppShell.vue

@@ -10,6 +10,7 @@ import { useUiStore } from "../stores/ui";
 import BaseModal from "./BaseModal.vue";
 import CommandPalette from "./CommandPalette.vue";
 import Icon from "./Icon.vue";
+import ExportNotes from "./ExportNotes.vue";
 import ImportNotes from "./ImportNotes.vue";
 import LabelsModal from "./LabelsModal.vue";
 import { isDesktop } from "../desktop/bridge";
@@ -484,10 +485,7 @@ async function signOut() {
           >
             <Icon name="calendar" /> Timeline
           </RouterLink>
-          <!-- Direct download (same-origin GET, session cookie sent); not a route. -->
-          <a href="/api/notes/export" download class="nav-link" title="Download all your notes as a zip">
-            <Icon name="download" /> Export
-          </a>
+          <ExportNotes />
           <ImportNotes />
 
           <!-- Account, settings and sign-out, for the screens where they are NOT in

frontend/src/components/DesktopIntegrationPrompt.vue

@@ -4,11 +4,13 @@ import BaseModal from "./BaseModal.vue";
 import BaseButton from "./BaseButton.vue";
 import { isDesktop, desktop } from "../desktop/bridge";
 import { useUiStore } from "../stores/ui";
+import { errorMessage } from "../api/errors";
 
 // First-run prompt (Linux AppImage only) offering to add Inkwell to the
 // applications menu so it behaves like an installed app instead of a loose file.
 // Shown once; the choice is remembered. Users who decline can integrate later from
-// Account. No-op on the web build and on already-integrated / non-AppImage runs.
+// the Sync page (DesktopMenuEntry). No-op on the web build and on already-integrated /
+// non-AppImage runs.
 const DISMISS_KEY = "desktop.integration.prompted";
 
 const ui = useUiStore();
@@ -38,7 +40,7 @@ async function integrate() {
     show.value = false;
     ui.showToast("Inkwell added to your applications menu.");
   } catch (e) {
-    ui.showToast((e as { message?: string }).message ?? "Couldn't add to applications.");
+    ui.showToast(errorMessage(e, "Couldn't add to applications."));
   } finally {
     working.value = false;
   }
@@ -60,7 +62,7 @@ async function integrate() {
       <p class="mt-2 text-sm text-neutral-600 dark:text-neutral-400">
         We'll add a menu entry so you can launch Inkwell from your app launcher, and keep a stable
         copy in <code class="font-mono text-xs">~/Applications</code> so it isn't lost from Downloads.
-        You can undo this any time from your account.
+        You can undo this any time from the Sync page.
       </p>
       <div class="mt-6 flex justify-end gap-3">
         <BaseButton variant="ghost" :disabled="working" @click="dismiss">Not now</BaseButton>

frontend/src/components/DesktopMenuEntry.vue

@@ -0,0 +1,58 @@
+<script setup lang="ts">
+import { onMounted, ref } from "vue";
+import BaseButton from "./BaseButton.vue";
+import { desktop, isDesktop, type IntegrationStatus } from "../desktop/bridge";
+import { errorMessage } from "../api/errors";
+import { useUiStore } from "../stores/ui";
+
+// The applications-menu entry for a Linux AppImage: add it, or take it away again.
+// Renders nothing anywhere else — the web, Windows, or an AppImage-less Linux build.
+//
+// It lived on the Account page, which the desktop app never shows: a toggle the
+// first-run prompt promised ("undo any time") with no way to reach it.
+const ui = useUiStore();
+const status = ref<IntegrationStatus | null>(null);
+const busy = ref(false);
+
+onMounted(async () => {
+  if (!isDesktop()) return;
+  try {
+    status.value = await desktop.integrationStatus();
+  } catch {
+    status.value = null;
+  }
+});
+
+async function toggle() {
+  busy.value = true;
+  try {
+    status.value = status.value?.is_integrated ? await desktop.unintegrate() : await desktop.integrate();
+    ui.showToast(
+      status.value?.is_integrated ? "Added to your applications menu." : "Removed from your applications menu.",
+    );
+  } catch (e) {
+    ui.showToast(errorMessage(e, "Couldn't update the menu entry."));
+  } finally {
+    busy.value = false;
+  }
+}
+</script>
+
+<template>
+  <section v-if="status?.is_appimage" class="mt-10 border-t border-neutral-200 pt-8 dark:border-neutral-800">
+    <h2 class="text-sm font-semibold">Applications menu</h2>
+    <div class="mt-3 flex items-center justify-between gap-4">
+      <p class="text-sm text-neutral-500 dark:text-neutral-400">
+        {{ status.is_integrated ? "Inkwell is in your applications menu." : "Not in your applications menu." }}
+      </p>
+      <BaseButton
+        :variant="status.is_integrated ? 'ghost' : 'primary'"
+        :loading="busy"
+        class="shrink-0"
+        @click="toggle"
+      >
+        {{ status.is_integrated ? "Remove" : "Add to applications" }}
+      </BaseButton>
+    </div>
+  </section>
+</template>

frontend/src/components/ExportNotes.vue

@@ -0,0 +1,38 @@
+<script setup lang="ts">
+import { ref } from "vue";
+import Icon from "./Icon.vue";
+import { repo } from "../adapters";
+import { errorMessage } from "../api/errors";
+import { useUiStore } from "../stores/ui";
+
+// Sidebar Export. In a browser the server streams the zip and the browser saves it;
+// on the desktop the core builds it from the local store with no server, saves it in
+// Downloads, and says exactly where.
+const ui = useUiStore();
+const busy = ref(false);
+
+async function run() {
+  if (busy.value) return;
+  busy.value = true;
+  try {
+    const savedTo = await repo.notes.exportAll();
+    if (savedTo) ui.showToast(`Exported to ${savedTo}`);
+  } catch (err) {
+    ui.showToast(errorMessage(err, "Export failed."));
+  } finally {
+    busy.value = false;
+  }
+}
+</script>
+
+<template>
+  <button
+    type="button"
+    class="nav-link w-full disabled:opacity-60"
+    :disabled="busy"
+    title="Save all your notes as a zip"
+    @click="run"
+  >
+    <Icon name="download" /> {{ busy ? "Exporting…" : "Export" }}
+  </button>
+</template>

frontend/src/components/FilterBar.vue

@@ -8,6 +8,7 @@ import type { NoteFacets } from "../stores/notes";
 import { facetCount, facetsFromQuery, facetsToQuery } from "../notes/facets";
 import { addLocalDays, formatLocalDay, parseLocalDate } from "../notes/datetime";
 import Icon from "./Icon.vue";
+import { errorMessage } from "../api/errors";
 
 // A dead-simple facet bar over the board: color + labels + has-reminder
 // + has-attachment + created-date range. The URL query IS the state, so a
@@ -71,7 +72,7 @@ async function saveView() {
     await savedFilters.create(name.trim(), facets.value);
     ui.showToast(`Saved view "${name.trim()}".`);
   } catch (e) {
-    ui.showToast((e as { error?: string }).error ?? "Couldn't save the view.");
+    ui.showToast(errorMessage(e, "Couldn't save the view."));
   }
 }
 

frontend/src/components/ImportNotes.vue

@@ -4,6 +4,7 @@ import Icon from "./Icon.vue";
 import { useNotesStore } from "../stores/notes";
 import { useLabelsStore } from "../stores/labels";
 import { useUiStore } from "../stores/ui";
+import { errorMessage } from "../api/errors";
 
 // Sidebar counterpart to Export: pick a .zip (an Inkwell export for round-trip,
 // or a Google Keep Takeout archive) and import its notes. Additive — never
@@ -31,7 +32,7 @@ async function onFile(e: Event) {
     const tail = res.skipped ? ` (${res.skipped} skipped)` : "";
     ui.showToast(`Imported ${res.imported} ${noun}${tail}.`);
   } catch (err) {
-    ui.showToast((err as { error?: string }).error ?? "Import failed.");
+    ui.showToast(errorMessage(err, "Import failed."));
   } finally {
     busy.value = false;
   }