refactor: make SpeedyBot v4 one integrated application

[roseshayan]

Why

The first v4 merge shipped the new product layer as app.py + speedybot_v4/, which made v4 look like an overlay instead of the actual application.

This PR makes v4 the single integrated SpeedyBot project.

Architecture

• main.py is again the one official production entrypoint.
• the existing business core moves to speedybot/core.py without functional rewriting;
• v4 modules move from speedybot_v4/ to the permanent version-independent speedybot/ package;
• app.py is removed;
• tests/test_v4_storage.py becomes tests/test_storage.py.

Complete-project deployment

• install.sh installs the complete repository layout;
• update.sh synchronizes the complete repository with rsync --delete instead of a hard-coded file list;
• .env, .venv, SQLite DB/WAL/SHM, backups and deployment state are preserved;
• obsolete version-specific source files are removed automatically;
• rollback restores the complete previous application plus runtime state;
• run.sh always executes /root/SpeedyBot/main.py.

Documentation

README English/Persian, migration notes, changelog and v4 release notes now describe the integrated architecture and the one-time updater refresh required for older installations.

Validation

• Python syntax for main.py and speedybot/*.py
• Unit tests
• Shell syntax
• CI layout check ensures app.py and speedybot_v4/ no longer exist
• Version remains 4.0.0

Maintainer: SudoShayanNA