Two chronic problems fall out:
1. **Split-brain config.** Admin edits DB via the panel; app boot ignores DB.
Migration completes; live backend hasn't moved. Admin has to remember to
copy env vars into `.env` and restart. Two sources of truth for the same
setting. Cutover is a manual multi-step flow; users routinely get it wrong.
2. **Migration data-loss window on concurrent writes.** The copy walks
`storage.blobs` in hash order. A blob whose hash is lex-lower than the
current cursor, written to source AFTER migration passed it, is never
copied to target. `passed=true, findings=0` completion does NOT guarantee
target has every blob. Silent.
3. **Migration target selection is fragile.** DTO passes the whole S3 config
at trigger time; secrets sit plaintext in `admin_settings`. Any future
pluggable-storage story compounds this (Azure, GCS, WebDAV-as-source, …).
This plan replaces the split-brain model with a single-source-of-truth
architecture:
- `.env` declares **N named storage entries** (immutable per-deploy).
- `admin_settings.storage.active_backend_name` holds ONE row — which named
entry the app currently runs on. That's the whole runtime config.
- Migration is the atomic transition from one active entry to another. Server
is put in read-only mode for the copy window; on completion, the active
pointer flips; a restart cuts over.
Edouard Vanbelle