feat(studio): rich theme picker (presets + custom colour) + editor 0.11.0

Settings dialog's Theme Plugin section is now a grid of
swatched tiles:

- Built-in (none) — falls back to FaiTheme.light/.dark
- One tile per installed studio.theme.* plugin, each
  showing the plugin's primary/secondary/tertiary as
  live colour dots. Tile loads its preview lazily so a
  dozen installed themes don't block the picker.
- Custom — opens a colour-picker dialog with 12 curated
  Material presets + a hex input + live preview. Selecting
  applies ColorScheme.fromSeed for both brightnesses.

main.dart's _pluginThemes parses a 'custom:#RRGGBB' sigil
in the same notifier slot as plugin capability ids, so the
existing persistence + restoration paths cover the custom
case with no new state.

Bumps editor to 0.11.0 (type-checked port connections +
dynamic card width fix + card-height border allowance) and
Studio to 0.58.0.

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

lib/l10n/app_localizations_en.dart

@@ -326,6 +326,25 @@ class AppLocalizationsEn extends AppLocalizations {
   String get themePluginEmpty =>
       'No theme plugins installed. Open the Store and pick one in the studio-plugin category.';
 
+  @override
+  String get themePluginCustom => 'Custom colour';
+
+  @override
+  String get themePluginCustomDialogTitle =>
+      'Custom theme — pick a seed colour';
+
+  @override
+  String get themePluginCustomHexLabel => 'Hex colour';
+
+  @override
+  String get themePluginCustomPreview => 'Live preview';
+
+  @override
+  String get themePluginCustomCancel => 'Cancel';
+
+  @override
+  String get themePluginCustomApply => 'Apply';
+
   @override
   String get settingsTitle => 'Hub endpoint';