core: shared notes on the desktop and phone, and Share from the desktop

The core pulls with shares from a server offering them (protocol 6): a note
says how it is held (owner, edit, view) and who shared it, and a revoked note
leaves the device. The first such pull starts the feed over once, so notes
shared before this build arrive. The store refuses what a share doesn't allow
(view: everything; edit: anything but the text), push sends only the text of
someone else's note, and their notes stay out of trash, reminders and
reordering. Unlinking drops them.

The Share dialog's calls go to the linked server over the device token, as
Tauri commands and through the FFI. The desktop now offers Share and "Shared
with me"; unlinked, the dialog says sharing needs a server.

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

frontend/src/adapters/local.ts

@@ -92,12 +92,12 @@ export const local: Repo = {
     rename: (id, name) => invoke<SavedFilter>("saved_filters_rename", { id, name }),
   },
 
-  // Sharing is between accounts on a server; the desktop gets it with sync (#5175).
-  // The Share controls are not shown here, so these only answer a stray call.
+  // Sharing is between accounts on a server, so these go to the linked one (#5175).
+  // Unlinked, each rejects with the core's explanation, which the dialog shows.
   shares: {
-    directory: () => Promise.resolve<Member[]>([]),
-    list: () => Promise.resolve<NoteShare[]>([]),
-    share: () => Promise.reject<NoteShare[]>(new Error(NEEDS_SERVER)),
-    unshare: () => Promise.reject<NoteShare[]>(new Error(NEEDS_SERVER)),
+    directory: () => invoke<Member[]>("shares_directory"),
+    list: (noteId) => invoke<NoteShare[]>("shares_list", { noteId }),
+    share: (noteId, userId, permission) => invoke<NoteShare[]>("shares_share", { noteId, userId, permission }),
+    unshare: (noteId, shareId) => invoke<NoteShare[]>("shares_unshare", { noteId, shareId }),
   },
 };

frontend/src/components/FilterBar.vue

@@ -9,7 +9,6 @@ import { facetCount, facetsFromQuery, facetsToQuery } from "../notes/facets";
 import { addLocalDays, formatLocalDay, parseLocalDate } from "../notes/datetime";
 import Icon from "./Icon.vue";
 import { errorMessage } from "../api/errors";
-import { isDesktop } from "../desktop/bridge";
 
 // 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
@@ -44,9 +43,6 @@ function toggleReminder() {
 function toggleAttachment() {
   patch({ has_attachment: facets.value.has_attachment ? undefined : true });
 }
-// Sharing is between accounts on a server, so the offline desktop has no shared notes
-// to narrow to (#5174).
-const sharingAvailable = !isDesktop();
 function toggleShared() {
   patch({ shared: facets.value.shared ? undefined : "with_me" });
 }
@@ -137,7 +133,6 @@ const chipOff = "border-neutral-300 text-neutral-600 hover:bg-neutral-100 dark:b
           Has attachment
         </button>
         <button
-          v-if="sharingAvailable"
           type="button"
           :class="[chipBase, facets.shared ? chipOn : chipOff]"
           @click="toggleShared"

frontend/src/components/NoteCard.vue

@@ -18,7 +18,6 @@ import { formatReminder, formatTrashCountdown, isOverdue, trashDaysLeft } from "
 import { useConfigStore } from "../stores/config";
 import { useUiStore } from "../stores/ui";
 import { canEditText, isOwnNote } from "../notes/sharing";
-import { isDesktop } from "../desktop/bridge";
 
 const props = defineProps<{ note: Note; reorderable?: boolean; active?: boolean }>();
 const emit = defineEmits<{
@@ -38,11 +37,12 @@ const config = useConfigStore();
 const ui = useUiStore();
 
 // --- Sharing (#5174). Someone else's note shows who shared it and offers none of
-// the owner's controls; at `view` its checkboxes are inert too. Sharing needs a
-// server, so the offline desktop has no Share button (its notes are all its own). ---
+// the owner's controls; at `view` its checkboxes are inert too. The desktop offers
+// Share as well: linked it goes through the server, unlinked the dialog says sharing
+// needs one (#5175). ---
 const own = computed(() => isOwnNote(props.note));
 const editable = computed(() => canEditText(props.note));
-const canShare = computed(() => own.value && !isDesktop());
+const canShare = own;
 const sharedLine = computed(() => {
   if (!own.value) {
     const who = props.note.shared_by?.display_name || "someone";

frontend/src/components/NoteEditor.vue

@@ -13,7 +13,6 @@ import type { Note, NoteLabel, NoteRevision } from "../stores/notes";
 import { labelChipClasses } from "../notes/colors";
 import { canEditText, isOwnNote } from "../notes/sharing";
 import { useUiStore } from "../stores/ui";
-import { isDesktop } from "../desktop/bridge";
 import {
   afterEnter,
   type EditorBlock,
@@ -123,7 +122,9 @@ const bodyPlaceholder = "Take a note…";
 const ui = useUiStore();
 const own = computed(() => isOwnNote(liveNote.value));
 const editable = computed(() => canEditText(liveNote.value));
-const canShare = computed(() => own.value && !isCreate.value && !isDesktop());
+// On the desktop too: linked, it shares through the server; unlinked, the dialog
+// says sharing needs one (#5175).
+const canShare = computed(() => own.value && !isCreate.value);
 const sharedLine = computed(() => {
   if (own.value) return "";
   const who = liveNote.value.shared_by?.display_name || "someone";