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/web/templates/layout.html

@@ -116,7 +116,7 @@
                 <li><a href="/settings/security" class="{{if eq .Page "settings-security"}}active{{end}}"><svg class="ico"><use href="#i-lock"/></svg>{{T "layout.biztonsag_es_hozzaferes"}}</a></li>
             </ul>
             <div class="sidebar-footer">
-                <span class="version">{{.Version}}</span>{{if .LangSwitch}}<form method="POST" action="/settings/language" class="lang-switch">{{.CSRFField}}<input type="hidden" name="back" value="{{.LangSwitchBack}}"><button type="submit" name="lang" value="hu" class="lang-switch-btn{{if eq .Lang "hu"}} active{{end}}" lang="hu">Magyar</button><button type="submit" name="lang" value="en" class="lang-switch-btn{{if eq .Lang "en"}} active{{end}}" lang="en">English</button></form>{{end}}
+                <span class="version">{{.Version}}</span>{{if .LangSwitch}}{{template "lang_globe" .}}{{end}}
                 {{if .AuthEnabled}}<a href="/logout" class="logout-link">{{T "layout.kijelentkezes"}}</a>{{end}}
             </div>
         </div>