The All/Photos/Videos/Raw tabs, the "12 photos" subtitle and the
"No favorite videos in June 2024" heading were still built from English
literals. Each heading is now a whole translatable sentence with a
{month} placeholder, and the subtitle uses plural forms.
Also fill in the French "Documents" search chip, which was left
untranslated because it matches the English word.
The app, the tray and the search prompt route every user-visible string
through GNU gettext in the `pdfs` text domain, with named placeholders and
plural forms. po/ holds the template, update and build scripts, and catalogs
for de, en_GB, es, fr, it, nl, pl and pt_BR. Preferences gains a Language row
that overrides the system language from the next start (config `language`).
Packages compile the catalogs into /usr/share/locale and the desktop files
carry translated descriptions and keywords. docs/TRANSLATING.md describes
the workflow.