[codex] port main ui toward ayugram layout

[lReDragol]

What changed

• ported the main Qt shell toward an AyuGram-style layout for the dialogs list, chat header, composer, and message bubbles
• added AyuGram-derived icon assets used by the new sidebar/header/composer rendering
• kept the existing Telegram logic and tests intact while changing the rendering layer

Why

• the previous ESCgram UI structure diverged heavily from the AyuGram source layout
• this branch moves the visible rendering much closer to the AyuGram visual model without pulling the Android source tree into the repo

Validation

• python -m compileall ui\main_window.py ui\chat_sidebar.py ui\chat_panels.py ui\message_widgets.py ui\ayugram_assets.py ui\export_dialog.py
• python -m pytest tests/test_chat_sidebar_sorting.py tests/test_message_widget_regressions.py tests/test_main_bootstrap.py tests/test_account_manager.py tests/test_auth_flow.py tests/test_telegram_lifecycle.py -q