R-359 + R-397: the off-site store gets checked, and the advertised check becomes real

Nothing ever verified that the off-site copies are still readable. The
whole-guest tier has verify jobs; the tier holding the customer's documents and
photos had none -- the complete set of restic verbs this controller used
contained no `check`. We would have found out at restore time, with a customer
waiting. On 2026-08-21 a deliberately damaged pack was caught at once by plain
`restic check`; we had never run it.

R-397: NotifyIntegrityOK/NotifyIntegrityFailed existed with no caller, the hub
allowlists both event types and carries the Hungarian text for both, the
settings checkbox exists, and the debug button posts to /api/debug/backup/
integrity. Everything was built except the part that runs. SIXTH instance of
that shape in this project.

THE HAZARD SHAPES THE WHOLE DESIGN. resticStep self-heals a crash lock by
running `unlock --remove-all` and retrying, and its own comment records why that
is safe: every caller holds the in-process single-flight mutex, so any lock it
meets is stale. A check that did not take that flag could meet a LIVE prune's
lock from this same box, remove it, and retry over the top of it. So the check
TAKES THE FLAG and SKIPS rather than waits -- waiting would pin the nightly
backup behind it, and a skip costs nothing because due-ness makes tomorrow try
again. TestR359_SkipsWhenRunningFlagHeld asserts the NON-EFFECTS: restic never
invoked, `unlock` never in any argv. Its red-proof prints the real thing --
restic running `check` while the flag was held.

DUE-NESS, NOT A WEEKDAY. Daily job, weekly behaviour: "is the last successful
check older than 7 days?" not "is it Sunday?". R-341 is exactly the other shape,
a dated check quietly missed and never caught up. No Weekly primitive added.

THREE OUTCOMES, NOT TWO. Skipped, Unreachable and failed are different facts.
"I could not look" is not "I looked and it is broken" -- R-339 already owns
reachability, and a second alarm for the same fact trains the operator to
discount the one alarm that means the backups are damaged. A timeout is
unreachable, never damage. A failure advances due-ness (a broken store must not
be re-checked nightly); a skip and an unreachable store do not.

Success is severity `info`, which severityNotifies DROPS -- it mails NOBODY, by
design. A weekly success e-mail is how people stop reading their alerts.

The customer gets a SENTENCE; restic's words go to the log, truncated (R-379:
615 bytes of raw database text reached a customer once). read-data-subset ships
OFF and a malformed value is refused at read time rather than handed to restic,
where one typo would fail the whole check.

Published on OffboxReportStatus, NOT on report.BackupReport's IntegrityOK --
those were retired by R-331 YESTERDAY and TestBackupReport_DeadFieldsStayZero
still passes unmodified.

Also: the monitoring page stopped promising a Sunday job that never existed, and
the debug button got its dispatch case.

PART 0 WAS NOT BUILT, AND R-398 WAS MY OWN MISTAKE. The seam it asked for
already exists: offboxRunner/SetOffboxRunner/m.runner() has been injectable
since the off-site tier shipped, and other tests drive restic-backed paths
through it. A resticStepFn seam would have been WORSE here -- it would replace
the `unlock --remove-all` escalation and hide it from the assertions that must
see it. R-358's AST ordering test is converted to a real execution test instead,
which immediately surfaced something the AST walk could not: unlockStale
legitimately runs before the restore.

Four red-proofs, each printing the pre-fix behaviour. Green gate: 28 packages,
rc 0. All 12 controller gates OK.

controller/internal/web/handler_debug.go

@@ -17,6 +17,7 @@ import (
 	"gitea.dooplex.hu/admin/felhom-controller/internal/agentapi"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/appexport"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/monitor"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/backup"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/report"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/system"
@@ -29,6 +30,15 @@ type DebugCallbacks struct {
 	HubConnectivityTest   func() (statusCode int, latencyMs int64, err error)
 	GiteaConnectivityTest func() (statusCode int, latencyMs int64, err error)
 	GetTelemetryPreview   func() ([]report.AppTelemetry, error)
+	// RunIntegrityCheck (R-359/R-397) runs the off-site integrity check SYNCHRONOUSLY and returns what
+	// it did. It is a callback rather than a direct call because the one implementation lives in
+	// main.go, where the manager and the notifier are both in scope — and there must be exactly one:
+	// a hand-run that diverged from the scheduled run is how a guard gets bypassed "because the
+	// operator asked for it", which is the specific hazard this feature is shaped around.
+	//
+	// `force` is the ONLY difference between the two callers. It skips the due-ness question and
+	// nothing else — every guard, above all the single-writer flag, applies identically.
+	RunIntegrityCheck func(force bool) backup.IntegrityResult
 }
 
 // debugPageHandler renders the debug dashboard page.
@@ -55,6 +65,12 @@ func (s *Server) handleDebugAPI(w http.ResponseWriter, r *http.Request) {
 	// Section 3: Backup testing (app-data only; disk-tier moved to host agent)
 	case subpath == "backup/dbdump" && r.Method == http.MethodPost:
 		s.debugTriggerDBDump(w, r)
+	// R-397 — the button at debug.html:83 has posted here since it was added and NOTHING answered.
+	// Verified 2026-08-30: this dispatch had no such case, so pressing „Restic integritás" did
+	// nothing at all. Seventh instance of built-but-never-wired in this project; filed as R-400 in its
+	// own right rather than disappearing inside this change.
+	case subpath == "backup/integrity" && r.Method == http.MethodPost:
+		s.debugRunIntegrityCheck(w, r)
 
 	// Section 5: Hub & connectivity
 	case subpath == "hub/push" && r.Method == http.MethodPost:
@@ -388,6 +404,43 @@ func (s *Server) debugTriggerDBDump(w http.ResponseWriter, r *http.Request) {
 	writeDebugJSON(w, http.StatusOK, true, "DB dump elindítva", nil)
 }
 
+// debugRunIntegrityCheck runs the off-site integrity check by hand (R-359/R-397).
+//
+// SYNCHRONOUS on purpose, unlike the DB-dump button beside it: the operator pressed this to learn an
+// ANSWER, and a fire-and-forget that returns „elindítva" would leave them reading logs for the result.
+// A structure check is seconds-to-minutes; its own timeout bounds it.
+//
+// Due-ness is IGNORED — "run it now" is the whole point of a button. Every other guard is intact,
+// including the single-writer flag, so a hand-run during a backup SKIPS exactly as the scheduled one
+// would. That is asserted by TestR397_DebugRunStillHonoursTheRunningFlag, because "the operator asked
+// for it" is precisely the reasoning that would reintroduce the hazard.
+func (s *Server) debugRunIntegrityCheck(w http.ResponseWriter, r *http.Request) {
+	if s.debugCallbacks == nil || s.debugCallbacks.RunIntegrityCheck == nil {
+		writeDebugJSON(w, http.StatusNotImplemented, false, "Nem bekötött", nil)
+		return
+	}
+	res := s.debugCallbacks.RunIntegrityCheck(true)
+	data := map[string]interface{}{
+		"ok":               res.OK,
+		"skipped":          res.Skipped,
+		"skip_reason":      res.SkipReason,
+		"unreachable":      res.Unreachable,
+		"duration_ms":      res.Duration.Milliseconds(),
+		"read_data_subset": res.ReadDataSubset,
+	}
+	switch {
+	case res.Skipped:
+		writeDebugJSON(w, http.StatusOK, true, "Kihagyva: "+res.SkipReason, data)
+	case res.Unreachable:
+		// NOT reported as a failure: the store could not be opened, so nothing was concluded about it.
+		writeDebugJSON(w, http.StatusOK, true, "A tároló nem érhető el — az ellenőrzés nem futott le", data)
+	case res.OK:
+		writeDebugJSON(w, http.StatusOK, true, "Az ellenőrzés rendben lezajlott", data)
+	default:
+		writeDebugJSON(w, http.StatusOK, false, "Az ellenőrzés hibát talált a tárolóban", data)
+	}
+}
+
 // ── Section 5: Hub & connectivity ───────────────────────────────────
 
 func (s *Server) debugHubPush(w http.ResponseWriter, r *http.Request) {