feat(workspace): backlinks at the end of a note

GET /documents/{id}/backlinks lists the notes the user can open whose
blocks link [[Title]] (also |alias and #section, case-insensitive),
excluding the note itself and the trash. The collapsible "Verlinkt auf
diese Notiz" section shows each note with folder and the linking bullets;
a click jumps straight to the bullet.

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

frontend/src/features/workspace/WorkspaceView.tsx

@@ -1583,6 +1583,7 @@ export const WorkspaceView: React.FC<WorkspaceViewProps> = ({
             onOpenShareModal={openDocShareModal}
             onSelectTag={handleSelectTag}
             onWikiLinkClick={handleWikiLinkClick}
+            onOpenDocBlock={handleJumpToDocBlock}
             onBackMobile={() => setMobileShowDetail(false)}
             onOpenTask={onOpenTask}
             onSaveStatusChange={(status, err) => {