simplify: dedupe boilerplate and remove dead code across all layers

lib/share_intent/pending_share.dart

@@ -1,3 +1,5 @@
+import 'package:flutter/foundation.dart';
+
 class PendingShare {
   final List<String> filePaths;
   final String? text;
@@ -17,12 +19,6 @@ class PendingShare {
   /// fires two `open(url)` requests per share (see ShareViewController), so
   /// the same share can arrive twice on the media stream — receivedAt is
   /// deliberately ignored here so such duplicates compare equal.
-  bool contentEquals(PendingShare other) {
-    if (text != other.text) return false;
-    if (filePaths.length != other.filePaths.length) return false;
-    for (var i = 0; i < filePaths.length; i++) {
-      if (filePaths[i] != other.filePaths[i]) return false;
-    }
-    return true;
-  }
+  bool contentEquals(PendingShare other) =>
+      text == other.text && listEquals(filePaths, other.filePaths);
 }