v0.254.0 — the saved notes follow the language, and the switch becomes a globe (R-557 slice 2 release C; SLICE 2 CLOSED)

The notes a background run SAVES — last night's backup line, the last error, the proof
result, the restore outcome — are written in the BOX's language at the moment they are
written. A household that switches sees the previous run's note in the old language until
the next run rewrites it: the operator's §16 option 1, stated rather than hidden.
EndRestoreOp no longer receives a Hungarian literal from anywhere.

The language switch is a globe. Two text links wrapped in the sidebar footer and asked the
reader to recognise "Magyar"/"English" as links; a globe is the one symbol every web user
already reads as "language", so nobody has to read Hungarian to escape Hungarian. It is
<details>/<summary> — a menu with no script, drawn inline because the icon sprite lives
only in layout.html and the visitor pages have their own shell.

Those visitor pages get the same globe, and a visitor's choice stays theirs: a display-only
felhom_lang cookie that langFor reads ONLY when there is no session. A signed-in household
can never inherit a language a previous visitor picked in the same browser. POST /lang is
CSRF-exempt for a narrow reason written at the exemption — its only achievable effect is the
language of the page the victim's own browser shows them — and safeBackPath refuses
//evil.example as well as https://, because "starts with /" alone is not the test. §16 taken:
a successful claim carries the cookie into the household's setting.

TWO PARITY EXCEPTIONS, MEASURED: 106 fixtures compared with a real diff — exactly two change
shapes (the dashboard footer, the globe in the shells) and 5 byte-identical, which are the
three pages that must not change.

I INTRODUCED A DEADLOCK AND THE SUITE CAUGHT IT BY HANGING. UpdateOffboxStatus holds the
settings write lock while running its callback; boxLang() wants the read lock; sync.RWMutex
is not reentrant. On a real box an off-site run would have hung forever HOLDING the settings
lock. Fixed by resolving the language before the callback, and guarded by a test that names
the file and line in a second instead of hanging for 25 minutes.

MinAgent: 0.131.0 (unchanged). No hub release needed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/backup/backup.go

@@ -13,8 +13,10 @@ import (
 	"time"
 
 	"gitea.dooplex.hu/admin/felhom-controller/internal/config"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/i18n"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/system"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/util"
 )
 
 // Manager orchestrates app-data backups: database dumps and Docker-volume tars.
@@ -1375,3 +1377,24 @@ func dbNames(dbs []DiscoveredDB) string {
 	}
 	return strings.Join(names, ", ")
 }
+
+// boxLang is the language a SAVED note is written in (release C, R-557 slice 2 option 1).
+//
+// A background run has no request and no reader, so it writes in the box's language at the moment it
+// writes. A household that switches sees last night's note in the old language until the next run
+// rewrites it — the operator's ruling, and the reason the reader never translates stored text.
+func (m *Manager) boxLang() string {
+	if m.settings == nil {
+		return i18n.Default
+	}
+	return m.settings.GetLanguage()
+}
+
+// note renders a saved note in the box's language.
+func (m *Manager) note(key string, args ...interface{}) string {
+	return util.Text(m.boxLang(), key, args...)
+}
+
+// noteErr renders an error into a saved note in the box's language: its bundle message when it
+// carries one (release B), its own text otherwise.
+func (m *Manager) noteErr(err error) string { return util.ErrText(m.boxLang(), err) }