i18n(home/search): localize TMDB genre names and discover row titles

[ReichiMD]

What

Same approach as #632, applied to the home screen and search.

Moves the remaining hardcoded English UI strings on the home screen and in
search into the string resource system and adds the German values. No
behaviour changes, no logic changes.

• the 27 TMDB genre names were kept as two separate English maps, one in
  HomeScreen.kt and one in SearchViewModel.kt. They now resolve from the
  numeric TMDB genre id through a shared helper (TmdbGenreNames.kt), so the
  home metadata rows and the search filter chips read from one place
• 12 of those 27 reused the existing collections_genre_* resources; 15 are
  new keys
• the five discover row titles (Trending, Popular This Year, Top Rated, New
  Releases, Hidden Gems) are localized for display only
• home: "Still loading your catalogue…" and "No description available." are
  new keys, "Retry" reuses the existing R.string.retry
• also fills seven values-de entries that were missing after the recent
  IPTV favourites and channel-variant work, so the German locale is complete
  again

Why

Approved in Discord (28 Aug): "Yes try to also bring hardcoded things into
this. That has been kinda a long time bug. They dont have to be in English
yea."

This benefits all 50 language folders, not just German — untranslated locales
fall back to English exactly as before.

Notes

• Stored values and internal keys are unchanged; only rendered text is
  localized. Follows the existing pattern from LiveCategory.kt.
• The English discover row title stays in Category.title on purpose: it is
  part of the category id used as the row's focus key.
• Movie and TV genre ids stay in separate lookups, matching the two maps that
  were there before, so no item gains or loses a genre label.
• Language names (COUNTRIES), brand names and animation labels are left
  untouched.
• Compile and unit tests verified green on CI.

created by Claude (Anthropic) on behalf of @ReichiMD