docs: reorder & testing

backend/internal/auth/deps.go

@@ -33,12 +33,12 @@ type UserEnsurer interface {
 }
 
 // GeoService provides the geo helpers auth needs at confirm-email-code:
-// a country lookup for the `preferred_language` fallback and a
-// post-commit write of `accounts.declared_country`. Both methods are
-// best-effort — auth never blocks the registration flow on geo failures.
+// a country lookup that backfills `accounts.declared_country` for newly
+// registered accounts and a post-commit write of the same column. Both
+// methods are best-effort — auth never blocks the registration flow on
+// geo failures.
 type GeoService interface {
 	LookupCountry(sourceIP string) string
-	LanguageForIP(sourceIP string) string
 	SetDeclaredCountryAtRegistration(ctx context.Context, userID uuid.UUID, sourceIP string) error
 }