v0.250.0: i18n slice 1 release C — the language switch on every dashboard page (R-556)

- addLanguageData: the v0.247.0 hide condition (switch only on non-Hungarian pages or with ?lang=) is
  deleted; every template is converted, so the offer no longer leads to a half-English page.
- 89 layout parity fixtures re-captured; each equals its predecessor plus exactly one switch form after
  the version span (checked byte-for-byte, 89 of 89). The 17 standalone fixtures are unchanged.
- TestLanguageSwitch_EndToEnd: a Hungarian household with no ?lang= sees the form (red-proofed by
  restoring the condition: this test and 89 parity cases fail).
- CHANGELOG v0.250.0, README §18, CONTEXT.

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

CONTEXT.md

@@ -9,6 +9,8 @@
 
 Last updated: 2026-09-17 (v0.247.0 — i18n spike: the dashboard can speak English, Hungarian byte-identical)
 
+> **2026-09-17 night — v0.250.0 (R-556 release C, slice 1 CLOSED).** All templates converted; the language switch is on every dashboard page (decision 6 superseded); login/claim/guest/catch-all through `executeTemplateLang`; Go-side messages and three app-name titles stay Hungarian (slice 2).
+
 > **2026-09-17 evening — v0.248.0 + v0.249.0 (R-556 releases A, B).** Apps/settings and backup pages
 > converted; `TestI18nParityCoversEveryMarker` (every marker rendered by a case); fixtures only written
 > when missing (`-update-i18n-golden`, `-i18n-golden-only`); `executeTemplateLang` for pages outside the