fix(studio): localize sidebar tooltips that stayed English

The connection-row tooltip, the _ConnectionLabel caption,
the footer settings tooltip, and the channel-pill explainer
were hardcoded English even when the running app was set to
German. Move all four through AppLocalizations.

Adds ARB strings (de + en):
 - connectionTapToStart      antippen zum Starten  / tap to start
 - sidebarSettingsTooltip    Einstellungen (Cmd-;) / Settings (Cmd-;)
 - sidebarChannelTooltip     multi-line channel explainer

Existing connectionConnected / connectionUnreachable /
connectionConnecting are reused as the caption pieces; only
those two new strings (plus the channel tooltip) needed
adding.

Version 0.51.7 -> 0.51.8.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_localizations_en.dart

@@ -192,6 +192,16 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get connectionStartHub => 'Start hub';
 
+  @override
+  String get connectionTapToStart => 'tap to start';
+
+  @override
+  String get sidebarSettingsTooltip => 'Settings (⌘;)';
+
+  @override
+  String get sidebarChannelTooltip =>
+      'Active channel — click to switch in Settings (⌘;).\nproduction = stable · beta = pre-release · dev = rolling · local = workspace';
+
   @override
   String get buttonCancel => 'Cancel';