chore(l10n): translate the pending catalog keys into the 18 languages

Fills the 26 untranslated keys (private feeds, per-podcast volume,
radio catalog, sleep-at-episode-end, playback errors, plus older ones
like Doublon/Se désabonner) across bg, cs, da, de, el, en, es, fi, hr,
hu, it, nl, pl, pt, ro, sk, sl and sv — 468 string units — and flags
the 11 non-translatable keys (format specifiers, brand names, example
URLs) with shouldTranslate=false. Machine-translated from the French
source; native review still welcome (see ROADMAP).

Co-Authored-By: Claude (RCA)