Add an opt-in 'centralized' sidecar storage mode alongside the default
'alongside' layout. In centralized mode, .metadata.json sidecars and
preview assets live under a configurable root (sidecar_storage_path,
default <settings_dir>/sidecars), mirroring the library-relative
directory structure: <root>/<library>/<root_basename>/<rel_dir>/.
Backend:
- settings: sidecar_storage_mode / sidecar_storage_path with validation;
changing either refreshes the preview allowlist
- config: centralized root added to preview-serving allowlist
- lifecycle: delete / move / rename / folder-rename / folder-delete and
undoable-delete staging all operate on the mirror tree in centralized
mode (model files themselves never move); EXDEV-tolerant cross-
filesystem moves
- scanners: pending-hash filesystem scan walks the mirror tree in
centralized mode; preview discovery reads from the sidecar dir;
.civitai.info stays co-located in both modes
- migration: SidecarMigrationUseCase moves sidecars+previews between
layouts both directions (keep-newer conflict resolution, preview_url
rewriting, WebSocket progress), exposed as POST+GET
/api/lm/sidecars/migrate with a mode guard (force=true for the
settings-first flow)
Frontend:
- settings modal: sidecar storage section (mode select + path input with
browse/validation), mode-change confirmation offering immediate
migration (force=true), and a 'Migrate Sidecars Now' action
- i18n keys synced to all locales ([TODO: Translate] placeholders)
Docs: metadata-json-schema.md gains a storage-location section;
AGENTS.md records the sidecar_paths helper convention.