core, web: pin, archive and reorder a note someone shared with you

Schema v12 adds notes.state_at: a recipient's own pin, archive and order are
stamped there instead of on updated_at, which stays the text's time. Push sends
them only to a server advertising `shared_state` (push::Accepts), a view share
included; the first pull at that level starts the feed over once so held copies
drop their owner's pins. The client speaks protocol 7 and lists `shares` and
`shared_state` among the features a server may lack.

The web card and editor offer pin, archive and drag on shared notes; share and
trash stay the owner's, and the board's trash key skips notes you don't own.

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

frontend/src/components/NoteEditor.vue

@@ -865,7 +865,8 @@ function revPreview(rev: NoteRevision): string {
           >
             <Icon name="history" />
           </button>
-          <template v-if="!isCreate && !liveNote.trashed && own">
+          <!-- Pin and archive are everyone's own on a shared note (#5176); trash is the owner's. -->
+          <template v-if="!isCreate && !liveNote.trashed">
             <button
               type="button"
               class="icon-btn"
@@ -884,6 +885,7 @@ function revPreview(rev: NoteRevision): string {
               <Icon name="archive" />
             </button>
             <button
+              v-if="own"
               type="button"
               class="icon-btn"
               title="Move to trash"