v0.247.0: i18n spike — the dashboard can speak English, Hungarian byte-identical

Message bundles (internal/i18n) expanded into templates before parsing, one
template set per language. Launcher, /backups, /apps/<slug> and the layout
converted; household language setting, POST /settings/language, ?lang= override,
report field. Parity test against fixtures captured from unconverted templates;
copy gates read templates expanded; new i18n_missing_gate.

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

controller/scripts/mojibake_gate.py

@@ -33,7 +33,7 @@ SIGNATURE = {
     "ˇ": "ˇ (caron — cp1250 round-trip)",
 }
 
-EXTS = (".html", ".css", ".js", ".go")
+EXTS = (".html", ".css", ".js", ".go", ".json")  # .json: the i18n bundles (v0.247.0) are copy
 
 
 def files():