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/nl/settings.ts

@@ -235,6 +235,7 @@ export const settings = {
   linuxWaylandTextRenderMinimal: 'Minimaal (standaard CSS-verzachting)',
   discordRichPresence: 'Discord Rich Presence',
   discordRichPresenceDesc: 'Toont het huidige nummer op je Discord-profiel. Discord moet daarvoor geopend zijn.',
+  discordRichPresenceNotice: 'Let op: dit is de in Psysonic ingebouwde Discord Rich Presence. Wil je liever de officiële Navidrome Discord Rich Presence-plug-in gebruiken, laat deze functie dan uitgeschakeld en schakel in plaats daarvan verderop op deze pagina „Weergeven in live-venster" in.',
   discordCoverSource: 'Hoesbron',
   discordCoverSourceDesc: 'Waar de albumhoes voor je Discord-profiel vandaan komt.',
   discordCoverNone: 'Geen (alleen app-icoon)',
@@ -249,6 +250,7 @@ export const settings = {
   discordTemplateName: 'Gebruikerslijst-regel (name)',
   nowPlayingEnabled: 'Weergeven in live-venster',
   nowPlayingEnabledDesc: 'Stuurt het huidige nummer naar de live-luisteraarsweergave van de server. Uitschakelen om geen afspeelgegevens te verzenden.',
+  nowPlayingPluginNote: 'Vereist bij gebruik van de officiële Navidrome Discord Rich Presence-plug-in.',
   enableBandsintown: 'Bandsintown-tourdata',
   enableBandsintownDesc: 'Toon aankomende concerten van de huidige artiest in het Info-tabblad. Gegevens komen van de openbare Bandsintown-API.',
   lyricsServerFirst: 'Server-songtekst voorrang geven',