i18n slice 1 release C: parity cases + fixtures captured from UNCONVERTED templates

storage, storage_network, storage_init, storage_attach, sharing, login, claim,
launcher_shared, launcher_share_password, catchall, debug. Case completeness checked with the
coverage probe on a trial conversion.

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

controller/internal/web/i18n_parity_test.go

@@ -280,6 +280,7 @@ func i18nCases() []i18nCase {
 	// Slice 1 (R-556): one file of cases per release, each captured from its unconverted templates.
 	base = append(base, i18nCasesA()...)
 	base = append(base, i18nCasesB()...)
+	base = append(base, i18nCasesC()...)
 	return base
 }