fix(train): Jellyfin over https alone, but on the phone itself (ADR 0030, D54)

An http address to another machine is refused as typed, saying why: over it the password, the token and what the person listens to went through the network in clear, and the music job, held by Android to https, retried for ever without a track. A Jellyfin on the phone (localhost, 127.0.0.1) stays reachable over http, the network security config allowing those two alone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/lib/l10n/app_en.arb

@@ -607,6 +607,7 @@
   "@musicServer": {"description": "The label of the server's address."},
   "musicConnect": "Connect",
   "musicBadAddress": "Enter the server's address, such as jellyfin.example.org.",
+  "musicInClear": "Train connects to Jellyfin over https only: http would send the password unencrypted. Use the server's https address.",
   "musicUnreachable": "The server can't be reached. Check the address and the connection.",
   "musicNotJellyfin": "There is no Jellyfin server at this address.",
   "musicRefused": "Jellyfin refused. Check the user name and password.",