msglist: Add “(you)” indicator for self user in DM conversations

Add a localized “(you)” label beside the self user’s display name in
direct-message conversation titles. This improves clarity when viewing
DMs, especially in contexts where the participant list may otherwise be
ambiguous.

Update the RecentDmConversationsItem title logic so that:
* In a self-DM (case []), append the localized youLabel to the self
  user’s name.
* In a 1:1 DM, append the label when the other participant is the self
  user (edge case where user IDs match).
* For multi-user DMs, retain the existing comma-joined list without a
  youLabel, preserving current behavior.

Update the test helper checkTitle() to match the new rendering
behavior. The helper now inspects the rendered Text widgets directly and
matches on startsWith(expectedText), making it robust when the title
contains WidgetSpans or the new youLabel.

Preserve existing TODO comments and layout behavior. All tests pass
locally.

Author: cybernova2

assets/l10n/app_en.arb

@@ -665,6 +665,10 @@
   "@unknownUserName": {
     "description": "Name placeholder to use for a user when we don't know their name."
   },
+ "youLabel": "(you)",
+    "@youLabel": {
+      "description": "Label shown after the current user's display name in direct messages."
+    },
   "dmsWithYourselfPageTitle": "DMs with yourself",
   "@dmsWithYourselfPageTitle": {
     "description": "Message list page title for a DM group that only includes yourself."

lib/generated/l10n/zulip_localizations.dart

@@ -1041,6 +1041,12 @@ abstract class ZulipLocalizations {
   /// **'(unknown user)'**
   String get unknownUserName;
 
+  /// Label shown after the current user's display name in direct messages.
+  ///
+  /// In en, this message translates to:
+  /// **'(you)'**
+  String get youLabel;
+
   /// Message list page title for a DM group that only includes yourself.
   ///
   /// In en, this message translates to:

lib/generated/l10n/zulip_localizations_ar.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsAr extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_de.dart

@@ -571,6 +571,9 @@ class ZulipLocalizationsDe extends ZulipLocalizations {
   @override
   String get unknownUserName => '(Nutzer:in unbekannt)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DNs mit dir selbst';
 

lib/generated/l10n/zulip_localizations_el.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsEl extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_en.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsEn extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_es.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsEs extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_fr.dart

@@ -568,6 +568,9 @@ class ZulipLocalizationsFr extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_he.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsHe extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';
 

lib/generated/l10n/zulip_localizations_hu.dart

@@ -552,6 +552,9 @@ class ZulipLocalizationsHu extends ZulipLocalizations {
   @override
   String get unknownUserName => '(unknown user)';
 
+  @override
+  String get youLabel => '(you)';
+
   @override
   String get dmsWithYourselfPageTitle => 'DMs with yourself';