refactor(backend/publisher): transformer pipeline + shared registry + shiki highlighting

refactor: remove MUI, unify publisher pipeline, add shared component registry

feat: adopt template CSS architecture, hero/TOC/color alignment

fix: authors, bibliography and CSS in published article

fix: resolve TipTap v3 collaboration crash

fix: adapt to StarterKit v3 API changes

refactor: store pre-computed attrs in citation/bibliography nodes

feat: add publish pipeline with HTML/PDF/thumbnail generation