feat(email-viewer): message spacing setting (auto/always/edge-to-edge)

components/settings/reading-settings.tsx

@@ -35,6 +35,7 @@ export function ReadingSettings() {
     hoverActionsCorner,
     hideInlineImageAttachments,
     attachmentImagePreviewsEnabled,
+    messageSpacing,
     updateSetting,
   } = useSettingsStore();
 
@@ -115,6 +116,20 @@ export function ReadingSettings() {
       </SettingItem>
       )}
 
+      {!isSettingHidden('messageSpacing') && (
+      <SettingItem label={t('message_spacing.label')} description={t('message_spacing.description')} locked={isSettingLocked('messageSpacing')}>
+        <Select
+          value={messageSpacing}
+          onChange={(value) => updateSetting('messageSpacing', value as typeof messageSpacing)}
+          options={[
+            { value: 'auto', label: t('message_spacing.auto') },
+            { value: 'always', label: t('message_spacing.always') },
+            { value: 'edge', label: t('message_spacing.edge') },
+          ]}
+        />
+      </SettingItem>
+      )}
+
       {!isSettingHidden('deleteAction') && (
       <SettingItem label={t('delete_action.label')} description={t('delete_action.description')} locked={isSettingLocked('deleteAction')}>
         <div className="flex flex-col gap-2">