docs: v0.124.0 backups IA restructure — CHANGELOG + REPORT + CONTEXT (decisions 1-3) + README page map + REUSE; records the HIGH containerized-.fab volume-strand finding and the agent SystemDisks legacy-boot finding

Claude-Session: https://claude.ai/code/session_01GzammAMzsJTgpQHqxwM2bC

REUSE.md

@@ -208,6 +208,8 @@ Cross-repo edges:
 - **New background job**: `sched.Every`/`sched.Daily` registration block in controller/cmd/controller/main.go.
 - **New template function**: `Server.templateFuncMap` (controller/internal/web/funcmap.go) — obey v2 state-suffix vocabulary.
 - **New page/nav item**: `baseData` + sidebar in controller/internal/web/templates/ (nested sub-links pattern `.nav-links-nested`); must pass `controller/scripts/template_id_gate.py` + `controller/scripts/emoji_gate.py` + `controller/scripts/native_confirm_gate.py` + `controller/scripts/offbox_rename_gate.py`.
+- **Guarded file download (v0.124.0)**: `handler_export_download.go` — the canonical shape for streaming a server-side file to the browser: accept a BASENAME only (shape regexp + no separators/`..`), `filepath.Join` then assert `filepath.Dir(path) == dir`, `io.Copy` (never ReadAll), `Content-Disposition: attachment`, remove after a successful stream, TTL sweep (`sweepFabDownloads(dir, now, maxAge, logger)` — now injected for tests). Red-proof the guard by loosening to prefix-matching (the `..` case must fail).
+- **Backups sub-page data**: `backupsCommonData(page, title, r)` + `backupsOffboxData(data)` (handlers.go) — the ONLY builders for the four `/backups*` pages; a new backups section extends these, never re-derives in a page handler. Section moves are gated by `scripts/backups_split_move_check.py` (one-shot vs df7ad37).
 - **Consequential-action confirm (LIGHT)**: `felhomConfirm(el, question, onYes)` in layout.html (v0.123.0) — the trigger swaps in place to "kérdés + Igen/Mégse"; form buttons opt in with `data-confirm="…"` (delegated listener, `requestSubmit` keeps formaction/name-value). NEVER native `confirm()`/`prompt()` (OS-modals freeze browser automation — drill F-11; `native_confirm_gate.py` enforces). Heavy destructive flows keep the `.confirm-overlay` `openDialog` pattern.
 - **New hub event**: typed `Notify*` wrapper on Notifier + hub allowlist entry (cross-repo).
 - **New app integration**: `integrations.Manager.RegisterHandler` with `IntegrationKey(provider, target)`.