feat(i18n): offer every ISO 639-1 language

The table was thirty languages typed by hand. It is now generated:
utils/generate_languages.py takes the 184 alpha-2 codes from pycountry,
the display names from CLDR through babel, and the writing direction from
CLDR character order. 159 languages carry their endonym; the remaining 25
have no CLDR entry and carry their English ISO name.

That corrects the right-to-left set, which had four entries and needs ten
— dv, ks, ps, sd, ug and yi were simply missed.

Only 29 languages ship an interface catalogue, so the other 155 render in
English until one is filled. make i18n-ui fills app/i18n/ui/ for them, and
make i18n now covers the interface strings as well; neither asks for a
string a shipped catalogue already answers, so hand-written entries stay.

184 entries do not fit on a screen, so the language menu scrolls inside
itself. overscroll-behavior keeps the page behind it from moving once the
list reaches its end.

babel and pycountry are dev dependencies: the generator needs them, the
application does not.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/templates/moduls/navigation.html.j2

@@ -103,7 +103,7 @@
                 <a class="nav-link dropdown-toggle btn btn-light" id="navbarDropdownLanguage" role="button" data-bs-toggle="dropdown" data-bs-display="dynamic" aria-expanded="false" title="{{ t('Language') }}">
                     <i class="fa-solid fa-language"></i> {{ languages[lang] }}
                 </a>
-                <ul class="dropdown-menu">
+                <ul class="dropdown-menu language-menu">
                     {% for code, endonym in languages.items() %}
                     <li>
                         <a class="dropdown-item {% if code == lang %}active{% endif %}"