Merge pull request #509 from hildebrandttk/feat/unified-mailbox-account-scope

Feat/unified mailbox account scope

Rework the sidebar "All accounts" into an account-bounded "Unified Mailbox"
by default, with cross-account merging as an opt-in (admin-gated) sub-option.
The standalone per-account "All Mail" virtual folder is folded into the unified
All mail / Unread / Starred entries.

Conflict resolution notes:
- stores/settings-store.ts: both main and this branch independently added a
  per-account default-identity (#507) migration at different versions (main v6,
  branch v7). Merged migration is version 7 using the refactored migrateSettings
  function; the unified-mailbox rework is guarded at `version < 7` so users who
  stopped at main's interim v6 identity bump still receive it, while the #507
  identity-map coercion stays at `version < 6` so their populated map is kept.
- stores/auth-store.ts: kept main's applyPreferredIdentity (superset with the
  pre-#507 legacy migration).
- stores/email-store.ts: removed the ALL_MAIL_MAILBOX_ID paths (folded into the
  unified views) while preserving main's plugin hooks (onSearchResults /
  onEmailsFetched); adopted advancedSearchCrossViewEmails for advanced cross-view
  search.
- components/settings/layout-settings.tsx: kept main's faviconUnreadBadge setting
  alongside the new unifiedCrossAccount toggle.
- integration/: union-merged the two independently-authored suites - branch suite
  is authoritative (matches new behavior) with main's shared-identity (#569) group
  infrastructure preserved.
- components/email/email-composer.tsx: dropped a duplicate data-testid attribute
  introduced by the auto-merge.

components/settings/layout-settings.tsx

@@ -118,19 +118,26 @@ function MailLayoutPreview({
 export function LayoutSettings() {
   const t = useTranslations('settings.appearance');
   const tEmail = useTranslations('settings.email_behavior');
-  const { toolbarPosition, showToolbarLabels, hideAccountSwitcher, showRailAccountList, enableUnifiedMailbox, includeGroupInUnified, enableAllMailView, allMailFolderIds, enableCrossUnreadView, enableCrossStarredView, enableCrossAllView, colorfulSidebarIcons, tintListRowsByTag, showFolderTotalCount, faviconUnreadBadge, mailLayout, proInterface, updateSetting } = useSettingsStore();
+  const { toolbarPosition, showToolbarLabels, hideAccountSwitcher, showRailAccountList, enableUnifiedMailbox, includeGroupInUnified, unifiedCrossAccount, allMailFolderIds, enableCrossUnreadView, enableCrossStarredView, enableCrossAllView, colorfulSidebarIcons, tintListRowsByTag, showFolderTotalCount, faviconUnreadBadge, mailLayout, proInterface, updateSetting } = useSettingsStore();
   const { isSettingLocked, isSettingHidden, isFeatureEnabled } = usePolicyStore();
   const accounts = useAccountStore(s => s.accounts);
   const activeAccountId = useAccountStore(s => s.activeAccountId);
   const mailboxes = useEmailStore(s => s.mailboxes);
   const hasGroupInboxes = useMemo(() => mailboxes.some(m => m.isShared), [mailboxes]);
-  const allMailViewAllowed = isFeatureEnabled('allMailViewEnabled');
-  // Cross-account "All accounts" views, each gated independently by the admin.
+  const connectedAccountCount = useMemo(() => accounts.filter(a => a.isConnected).length, [accounts]);
+  const unifiedCrossAccountAllowed = isFeatureEnabled('unifiedCrossAccountEnabled');
+  // Unified Mailbox entries (All mail / Unread / Starred), each gated independently
+  // by the admin. Scope (single account vs. cross-account) is governed by
+  // `unifiedCrossAccount`; the folder picker below narrows which own folders feed them.
   const crossViews = [
     { setting: 'enableCrossUnreadView', value: enableCrossUnreadView, allowed: isFeatureEnabled('crossUnreadViewEnabled'), labelKey: 'cross_unread.label', descKey: 'cross_unread.description' },
     { setting: 'enableCrossStarredView', value: enableCrossStarredView, allowed: isFeatureEnabled('crossStarredViewEnabled'), labelKey: 'cross_starred.label', descKey: 'cross_starred.description' },
     { setting: 'enableCrossAllView', value: enableCrossAllView, allowed: isFeatureEnabled('crossAllViewEnabled'), labelKey: 'cross_all.label', descKey: 'cross_all.description' },
   ] as const;
+  // The folder picker narrows the own folders included in the entries above; show
+  // it once the user has enabled at least one of them.
+  const anyCrossEnabled = enableCrossUnreadView || enableCrossStarredView || enableCrossAllView;
+  const anyCrossAllowed = crossViews.some(c => c.allowed);
 
   // Own (non-shared) folders and the active account's All Mail selection. The
   // selection is per account: a missing entry = never configured, which
@@ -251,6 +258,21 @@ export function LayoutSettings() {
         </SettingItem>
       )}
 
+      {enableUnifiedMailbox && connectedAccountCount > 1 && unifiedCrossAccountAllowed && !isSettingHidden('unifiedCrossAccount') && (
+        <div className="ml-4 border-l-2 border-border pl-4 -mt-2">
+          <SettingItem
+            label={t('unified_mailbox.cross_account.label')}
+            description={t('unified_mailbox.cross_account.description')}
+            locked={isSettingLocked('unifiedCrossAccount')}
+          >
+            <ToggleSwitch
+              checked={unifiedCrossAccount}
+              onChange={(v) => updateSetting('unifiedCrossAccount', v)}
+            />
+          </SettingItem>
+        </div>
+      )}
+
       {enableUnifiedMailbox && hasGroupInboxes && !isSettingHidden('includeGroupInUnified') && (
         <div className="ms-4 border-s-2 border-border ps-4 -mt-2">
           <SettingItem
@@ -266,8 +288,9 @@ export function LayoutSettings() {
         </div>
       )}
 
-      {enableUnifiedMailbox && crossViews.some(c => c.allowed) && (
+      {enableUnifiedMailbox && anyCrossAllowed && (
         <div className="ms-4 border-s-2 border-border ps-4 -mt-2 space-y-2">
+
           {crossViews.map(({ setting, value, allowed, labelKey, descKey }) => (
             allowed && !isSettingHidden(setting) && (
               <SettingItem
@@ -286,21 +309,9 @@ export function LayoutSettings() {
         </div>
       )}
 
-      {allMailViewAllowed && !isSettingHidden('enableAllMailView') && (
-        <SettingItem
-          label={t('all_mail.label')}
-          description={t('all_mail.description')}
-          locked={isSettingLocked('enableAllMailView')}
-        >
-          <ToggleSwitch
-            checked={enableAllMailView}
-            onChange={(v) => updateSetting('enableAllMailView', v)}
-          />
-        </SettingItem>
-      )}
-
-      {allMailViewAllowed && enableAllMailView && (
+      {enableUnifiedMailbox && anyCrossAllowed && anyCrossEnabled && (
         <div className="ms-4 border-s-2 border-border ps-4 -mt-2 space-y-2">
+
           <div>
             <div className="text-sm font-medium text-foreground">{t('all_mail.folders_label')}</div>
             <div className="text-xs text-muted-foreground">{t('all_mail.folders_description')}</div>