feat: phase 2 — i18n messages EN/FR (--lang, AM_LANG/LANG, catalogue tr/tr_fmt, REPL lang) (closes #74)

tests/tip_test.rs

@@ -8,7 +8,9 @@ use clap::Parser;
 
 #[test]
 fn tip_page_renders_header_sections_and_options() {
-    let app = common::test_app("tip", &["tip"]);
+    // Issue #74: the page follows the locale; force French here so the
+    // assertions are deterministic whatever the host LANG says.
+    let app = common::test_app("tip", &["--lang", "fr", "tip"]);
     let text = tip_cmd::render(&app, false);
     assert!(text.contains("TIP"), "header missing:\n{text}");
     assert!(text.contains("antisèche"), "subtitle missing:\n{text}");