Add encrypted multi-user server management

[Opselon]

Summary

• scope server records to each Telegram user, add plan-based limits, and encrypt stored secrets with a Fernet key
• update the bot UI and localization so every add/remove server control is translated and available to non-admin users while still gating backups/updates to the primary admin
• rework the SSH manager and database/tests to understand the new per-user APIs and ensure premium plans can register more servers safely

Testing

• pytest tests/test_database.py tests/test_ssh_manager.py

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Migrate existing servers to new owner_id scope

The new user scoping queries in get_all_servers now filter rows by owner_id, but initialize_database only adds the owner_id column with a default of 0 for pre‑existing tables and never backfills it to the current Telegram IDs. On upgrade, all legacy servers keep owner_id=0, so calls like connect_server_menu that pass the real user id will see an empty list and report “no servers configured” until every server is re‑added. A migration/backfill for existing rows (e.g., assigning them to the admin user) or a fallback when owner_id=0 is required to preserve existing servers.

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