v0.148.0 — coherent snapshot pairs + an offsite restore that actually restores (R-43 + R-44)

Closes the two findings from DIAG-immich-restore-2026-07-19. Viktor deleted 11
immich photos to test offsite restore; both runs flashed success and the photos
stayed gone. Two independent defects.

R-43 — no offsite path could restore a database. All three buttons were
file-only: the two "visszaállítás" actions staged to a scratch folder and never
touched postgres, and place-to-live merged only MISSING files. For a DB-indexed
app the bytes returned and the app still could not see them. The dump was
carried INTO every snapshot and could never be replayed OUT of one.

New ReconstituteFromOffsite (/backup/offbox/reconstitute): safety dump → stop →
files overwritten to the snapshot version → start → the snapshot's own dump
replayed → health wait. Two invariants:
  - nothing is ever deleted (-a, no --ignore-existing, no --delete): a file
    created after the snapshot survives as an extra;
  - the undo exists before the act — the pre-restore- dump is verified ON DISK
    before anything is stopped, overwritten or replayed; if it cannot be taken
    the operation refuses with zero changes.
The replay reads the SCRATCH unit: the live unit is never overwritten, so
replaying from it would replay the current DB over itself and restore nothing.

R-44 — a manual push shipped an unrefreshed dump (up to ~24h old). That day's
predated the customer's account by four hours and probed to asset:0/user:0/
album:0 inside 52MB whose bulk was immich's shipped geodata. Every run, manual
AND nightly, now refreshes dumps + units BEFORE capturing. Order is the
mechanism: the gap can only ADD files the DB does not reference yet, never
remove one it does. Manifests carry offsite_run_id + dumps_at, so coherence is
verifiable at restore time rather than assumed; the periodic refresh carries a
prior stamp forward and never invents one.

Honesty surfaces, all warn-level and none a gate: unstamped (pre-v0.148) pairs
report their skew, ValidateDump gained an EXACT-match accounts-table sniff for
customer-empty dumps, the completion flash states an outcome instead of a
mechanism, and the missing-only button now says what it does NOT do.

11 tests; 5 red-proofs run and reverted. Two of those found real test weaknesses
rather than confirming strength — the first undo mutation was caught by a second
guard, and the first table-matching test did not discriminate between the two
matchers at all. Both tests were rewritten to the cases that separate them.

NOT in scope: R-41's catalog invariant check, nightly cadence, retention, quota
math, tier-2, and v0.147.x progress semantics beyond one added phase line.

Live acceptance (§9) has NOT run: no capability-map flip, customer-restore row
stays MISSING, R-3 stays DRAFT.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P9Nn14TWGzKoqAJAiVwC2s

controller/internal/web/handlers.go

@@ -815,6 +815,17 @@ func (s *Server) backupsRestoreHandler(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 	data["OffboxScratchReady"] = ready
+	// R-43: the same prepared scratch also enables the TRUE restore (files + database). Its confirm
+	// has to state what the pair actually IS — how old the DB half is, whether the two halves even
+	// come from the same run, and whether the dump looks customer-empty — because a restore is the
+	// one operation whose result the customer cannot inspect until after committing to it.
+	pairs := map[string]backup.OffsitePairInfo{}
+	if s.backupMgr != nil {
+		for name := range ready {
+			pairs[name] = s.backupMgr.OffsiteScratchPair(name)
+		}
+	}
+	data["OffboxPairInfo"] = pairs
 	// R-7b: the shares source is not an app — it has no per-app toggle and no recovery unit — so it
 	// gets its own restore entry rather than a synthetic row in OffboxApps (which would also make it
 	// appear in the per-app offsite TOGGLE list on /backups/remote, where it does not belong).