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>

build.py

@@ -64,6 +64,9 @@ def build():
         "--windowed",
         f"--name={__app_name__}",
         "--add-data", f"config/servers.example.json{os.pathsep}config",
+        "--add-data", f"tools/ssh.py{os.pathsep}tools",
+        "--add-data", f"tools/skill-ssh.md{os.pathsep}tools",
+        "--add-data", f"core/encryption.py{os.pathsep}core",
     ]
 
     # Icon
@@ -75,6 +78,7 @@ def build():
     cmd_parts.extend([
         "--hidden-import", "customtkinter",
         "--hidden-import", "PIL",
+        "--hidden-import", "pyotp",
         "--collect-all", "customtkinter",
     ])