v0.1.0 of steganography

Flutter plugin for encrypting text (AES-256-GCM, GOST Magma CTR) and hiding it in PNG/JPEG images using native LSB and JPEG-DCT steganography on Android and iOS. Changelog excerpt: - Initial release. - SteganographyController— encrypt/decrypt text with a 32-byte key. - Four steganography methods: LSB, DCT, TelegramRobust2, DCT Residual Modulation. - Payload encryption: AES-256-GCM and GOST R 34.12-2015 Magma (CTR). - Native JPEG coefficient embedding via libjpeg-turbo (Android/iOS).