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.dart

@@ -662,6 +662,42 @@ abstract class AppLocalizations {
   /// **'No theme plugins installed. Open the Store and pick one in the studio-plugin category.'**
   String get themePluginEmpty;
 
+  /// No description provided for @themePluginCustom.
+  ///
+  /// In en, this message translates to:
+  /// **'Custom colour'**
+  String get themePluginCustom;
+
+  /// No description provided for @themePluginCustomDialogTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Custom theme — pick a seed colour'**
+  String get themePluginCustomDialogTitle;
+
+  /// No description provided for @themePluginCustomHexLabel.
+  ///
+  /// In en, this message translates to:
+  /// **'Hex colour'**
+  String get themePluginCustomHexLabel;
+
+  /// No description provided for @themePluginCustomPreview.
+  ///
+  /// In en, this message translates to:
+  /// **'Live preview'**
+  String get themePluginCustomPreview;
+
+  /// No description provided for @themePluginCustomCancel.
+  ///
+  /// In en, this message translates to:
+  /// **'Cancel'**
+  String get themePluginCustomCancel;
+
+  /// No description provided for @themePluginCustomApply.
+  ///
+  /// In en, this message translates to:
+  /// **'Apply'**
+  String get themePluginCustomApply;
+
   /// No description provided for @settingsTitle.
   ///
   /// In en, this message translates to: