feat: integrate Flutter Quill for rich text editing and update note handling

- Added Flutter Quill package for rich text editing capabilities.
- Refactored note body handling to support Quill's Document format.
- Updated note editor screen to use QuillEditor and QuillController.
- Enhanced note search functionality to convert note body to plain text.
- Modified note card display to show plain text from note body.
- Updated localization support for Quill in the app.
- Registered necessary plugins for URL launching and file selection on all platforms.
- Updated app icons and other assets for consistency across platforms.
- Updated pubspec.yaml and pubspec.lock to include new dependencies and versions.

lib/data/note_body.dart

@@ -0,0 +1,38 @@
+import 'dart:convert';
+
+import 'package:flutter_quill/flutter_quill.dart';
+
+Document noteBodyToDocument(String storedBody) {
+  final String trimmedBody = storedBody.trimLeft();
+
+  if (trimmedBody.startsWith('[')) {
+    try {
+      final dynamic decoded = jsonDecode(storedBody);
+      if (decoded is List) {
+        return Document.fromJson(decoded);
+      }
+    } catch (_) {
+      // Fall back to plain text for legacy notes or malformed JSON.
+    }
+  }
+
+  if (storedBody.isEmpty) {
+    return Document();
+  }
+
+  final String plainText = storedBody.endsWith('\n')
+      ? storedBody
+      : '$storedBody\n';
+
+  return Document.fromJson(<dynamic>[
+    <String, String>{'insert': plainText},
+  ]);
+}
+
+String noteBodyToPlainText(String storedBody) {
+  return noteBodyToDocument(storedBody).toPlainText();
+}
+
+String noteDocumentToStorageJson(Document document) {
+  return jsonEncode(document.toDelta().toJson());
+}