Replace image_gallery_saver with image_gallery_saver_plus to fix Android build error

[krishna3554]

Motivation

• The Android Gradle Plugin produced a namespace error for image_gallery_saver-2.0.3; switching to a maintained package avoids the AGP namespace failure and updates the media-saving API.

Description

• Replace the image_gallery_saver dependency with image_gallery_saver_plus: ^4.0.1 in pubspec.yaml.
• Update lib/core/utils/media_saver.dart to import package:image_gallery_saver_plus/image_gallery_saver_plus.dart and call ImageGallerySaverPlus.saveImage and ImageGallerySaverPlus.saveFile for photo/video saves.

Testing

• Verified the substitution with rg "image_gallery_saver" pubspec.yaml lib which shows the new package and updated import (succeeded).
• Checked for Flutter on the host with flutter --version, which could not run because Flutter is not installed in this environment (automated check failed).
• Attempted an Android build check with JAVA_HOME=$HOME/.local/share/mise/installs/java/17.0.2 PATH=$JAVA_HOME/bin:$PATH gradle -p android help, which failed because android/local.properties is missing in this checkout (automated build could not complete).

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Codex Task