v1.2.0 + v1.3.0: Localization, About dialog, TOTP/2FA, stability improvements

v1.2.0:
- GUI localization (EN/RU/ZH) with language switcher and persistent selection
- About dialog (ⓘ) with app info, features, quick start guide
- core/i18n.py — internationalization module with t() function
- All GUI components translated via t() keys

v1.3.0:
- TOTP/2FA tab — Google Authenticator compatible codes with live 30s countdown,
  one-click copy, per-server secret management
- core/totp.py — TOTP module (pyotp, RFC 6238)
- core/logger.py — rotating file logger (5MB, 3 backups)
- Stronger Fernet encryption key with automatic migration from old key
- Thread-safe server store with locks, atomic writes, auto-restore on corruption
- Parallel status checks via ThreadPoolExecutor (up to 10 concurrent)
- SSH client: explicit channel cleanup, Unix key permissions
- Server dialog: port validation (1-65535), TOTP secret field
- Language change preserves active tab and server selection
- pyotp dependency added

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,59 @@
 # Changelog
 
+## [1.3.0] - 2026-02-23
+
+### Added
+- **TOTP / 2FA tab** — Google Authenticator compatible codes with live 30-second countdown
+  - Per-server TOTP secret storage (encrypted alongside passwords)
+  - One-click code copy to clipboard
+  - Color-coded countdown (green → yellow → red)
+  - Generate random secrets or paste existing ones
+  - TOTP secret field in server add/edit dialog
+- `core/totp.py` — TOTP module (pyotp, RFC 6238)
+- `core/logger.py` — rotating file logger (5 MB, 3 backups)
+- `pyotp` dependency in requirements.txt
+
+### Changed
+- **Encryption**: new stronger Fernet key with automatic migration from old key
+- **Server store**: thread-safe file writes with locks, atomic saves (tmp + rename), auto-restore from backup on corruption
+- **Status checker**: parallel server checks via ThreadPoolExecutor (up to 10 concurrent)
+- **SSH client**: explicit channel cleanup in finally blocks, Unix key permissions (0o600)
+- **Server dialog**: port range validation (1-65535), TOTP secret field
+- `version.py` → 1.3.0
+
+## [1.2.0] - 2026-02-23
+
+### Added
+- About dialog (ⓘ button in header bar) with app info, features, and quick start guide
+- GUI localization: English, Russian (Русский), Chinese (中文)
+- Language switcher in header bar with persistent selection
+- `core/i18n.py` — internationalization module with full translation dictionaries
+- `gui/about_dialog.py` — CTkToplevel About window
+
+### Changed
+- All GUI components use `t()` translation function for all user-visible strings
+- `server_store.py` saves/loads language preference in settings.json
+- `version.py` → 1.2.0
+- Tabs, sidebar, dialogs, and all tab contents fully translated
+
+## [1.1.0] - 2026-02-23
+
+### Added
+- Fernet encryption for servers.json (passwords no longer stored in plaintext)
+- Automatic migration: first launch encrypts existing servers.json, creates pre-encryption backup
+- Manual and automatic backups (auto-backup every 10 min on save)
+- Backup restore from GUI (Setup tab → Configuration section)
+- Configurable config path (change servers.json location via GUI)
+- Settings persistence in settings.json
+- Encryption module installed alongside ssh.py for CLI support
+- `cryptography` dependency
+
+### Changed
+- server_store.py: encrypted read/write, settings management, backup logic
+- ssh.py: encryption-aware load/save with fallback for missing encryption module
+- claude_setup.py: installs encryption.py alongside ssh.py
+- setup_tab.py: Configuration section with path selector, backup/restore controls, encryption status
+
 ## [1.0.0] - 2026-02-23
 
 ### Added