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

controller/internal/web/i18n_web.go

@@ -20,18 +20,13 @@ import (
 
 // addLanguageData puts the request's language and the switch state into a page's data.
 //
-// The switch is shown only when the page is NOT in Hungarian, or the request carries ?lang=. That is a
-// deliberate property of this release, not an oversight: English covers three pages, so offering it to
-// every household would put a half-English dashboard one click away. A Hungarian household therefore
-// sees nothing new; the way back from English is always on screen. Slice 1 of the plan makes the
-// switch visible to everyone once the remaining pages are converted.
+// The switch is on every dashboard page, in every language (v0.250.0, slice 1 release C). Until then it
+// was hidden from Hungarian pages without ?lang=, because English covered only part of the dashboard;
+// every template is converted now, so the offer no longer leads to a half-English page. Pinned by
+// TestLanguageSwitch_EndToEnd (a Hungarian household with no ?lang= sees the form).
 func (s *Server) addLanguageData(data map[string]interface{}, r *http.Request, lang string) {
 	data["Lang"] = lang
-	show := lang != i18n.Default
-	if r != nil && r.URL.Query().Get("lang") != "" {
-		show = true
-	}
-	if show && r != nil {
+	if r != nil {
 		data["LangSwitch"] = true
 		data["LangSwitchBack"] = r.URL.Path
 	}