Fullscreen player polish + Discord Rich Presence fixes (#1068)

* fix(fullscreen-player): drop track-number prefix from title, stop clipping descenders

The big title showed a zero-padded queue position ("11. ") before the
song name; remove it (the position still lives in the top bar). Also bump
line-height 1.05 -> 1.25 so overflow:hidden no longer crops descenders
(g, j, p, q, y) at 46px.

* feat(settings): clarify built-in Discord RP vs official Navidrome plugin

Add a bold notice atop the Discord Rich Presence block explaining it is
the built-in integration, and that users wanting the official Navidrome
Discord RP plugin should leave it off and enable "Show in Now Playing"
instead. Add a matching bold note to the Now Playing setting. New i18n
keys discordRichPresenceNotice / nowPlayingPluginNote across all 5 locales.

* fix(discord-rp): use HTTPS cover URL instead of local file:// path

Discord Rich Presence images are fetched by Discord's servers, so
large_image must be a key or an https:// URL they can reach. Since the
cover pipeline moved to an on-disk webp cache, coverArtUrlForDiscord
returned a file://.../800.webp path on cache hit, which Discord cannot
load and silently falls back to the app icon. Always hand it the
getCoverArt URL; MPRIS keeps the local file:// path unchanged.

* i18n(settings): fill discordRichPresenceNotice + nowPlayingPluginNote for es, nb, ro, ru

The two new Discord-RP notice keys had only landed in 5 of the 9 locales;
complete the set so no locale falls back to English.

* docs(changelog): fullscreen title + Discord RP fixes (PR #1068)

src/locales/nb/settings.ts

@@ -234,6 +234,7 @@ export const settings = {
   linuxWaylandTextRenderMinimal: 'Minimum (standard CSS-utjevning)',
   discordRichPresence: 'Discord Rich Presence',
   discordRichPresenceDesc: 'Vis sporet som spilles i din Discord-profil. Krever at Discord kjører.',
+  discordRichPresenceNotice: 'Merk: dette er den innebygde Discord Rich Presence i Psysonic. Vil du heller bruke det offisielle Navidrome Discord Rich Presence-tillegget, la denne funksjonen være av og aktiver i stedet «Vis i "Nå spiller"» lenger ned på denne siden.',
   discordCoverSource: 'Coverkilde',
   discordCoverSourceDesc: 'Hvor albumcoveret for Discord-profilen din hentes fra.',
   discordCoverNone: 'Ingen (kun app-ikon)',
@@ -248,6 +249,7 @@ export const settings = {
   discordTemplateName: 'Brukerliste-linje (name)',
   nowPlayingEnabled: 'Vis i "Nå spiller"',
   nowPlayingEnabledDesc: 'Send sporet som spilles av til tjenerens live-lyttervisning. Deaktiver for å stoppe sending av avspillingsdata.',
+  nowPlayingPluginNote: 'Nødvendig ved bruk av det offisielle Navidrome Discord Rich Presence-tillegget.',
   enableBandsintown: 'Bandsintown-turnédatoer',
   enableBandsintownDesc: 'Vis kommende konserter for gjeldende artist i Info-fanen. Data hentes fra det offentlige Bandsintown-API-et.',
   lyricsServerFirst: 'Foretrekk server-sangtekst',