Fix all build/type/lint errors, write 60 new tests (175 total),
update seed with new widget types and team board permissions,
install missing svelte-i18n dependency, fix DynamicIcon for Svelte 5.
- Add OIDC/OAuth2 login via openid-client with PKCE flow
- Auto-provision OAuth users with group mapping
- Conditional login page (OAuth/local/both based on auth mode)
- Admin OAuth test connection button
- Install svelte-dnd-action for board editor DnD
- Draggable sections and widgets with cross-section moves
- Reorder APIs with atomic Prisma transactions
- Visual drag handles and drop zone indicators