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>

gui/sidebar.py

@@ -3,6 +3,7 @@ Sidebar — server list with search, add/edit/delete buttons.
 """
 
 import customtkinter as ctk
+from core.i18n import t
 from gui.widgets.status_badge import StatusBadge
 
 
@@ -18,14 +19,14 @@ class Sidebar(ctk.CTkFrame):
         self.pack_propagate(False)
 
         # Title
-        title = ctk.CTkLabel(self, text="Servers", font=ctk.CTkFont(size=18, weight="bold"))
-        title.pack(padx=15, pady=(15, 5))
+        self.title_label = ctk.CTkLabel(self, text=t("servers"), font=ctk.CTkFont(size=18, weight="bold"))
+        self.title_label.pack(padx=15, pady=(15, 5))
 
         # Search
         self.search_var = ctk.StringVar()
         self.search_var.trace_add("write", lambda *_: self._refresh_list())
-        search = ctk.CTkEntry(self, placeholder_text="Search...", textvariable=self.search_var)
-        search.pack(fill="x", padx=10, pady=(5, 10))
+        self.search_entry = ctk.CTkEntry(self, placeholder_text=t("search"), textvariable=self.search_var)
+        self.search_entry.pack(fill="x", padx=10, pady=(5, 10))
 
         # Server list
         self.list_frame = ctk.CTkScrollableFrame(self, fg_color="transparent")
@@ -34,11 +35,11 @@ class Sidebar(ctk.CTkFrame):
         # Buttons
         btn_frame = ctk.CTkFrame(self, fg_color="transparent")
         btn_frame.pack(fill="x", padx=10, pady=10)
-        self.add_btn = ctk.CTkButton(btn_frame, text="+ Add", width=70, height=30, command=self._on_add)
+        self.add_btn = ctk.CTkButton(btn_frame, text=t("add"), width=70, height=30, command=self._on_add)
         self.add_btn.pack(side="left", padx=(0, 3))
-        self.edit_btn = ctk.CTkButton(btn_frame, text="Edit", width=70, height=30, fg_color="#6b7280", command=self._on_edit)
+        self.edit_btn = ctk.CTkButton(btn_frame, text=t("edit"), width=70, height=30, fg_color="#6b7280", command=self._on_edit)
         self.edit_btn.pack(side="left", padx=3)
-        self.del_btn = ctk.CTkButton(btn_frame, text="Delete", width=70, height=30, fg_color="#ef4444", hover_color="#dc2626", command=self._on_delete)
+        self.del_btn = ctk.CTkButton(btn_frame, text=t("delete"), width=70, height=30, fg_color="#ef4444", hover_color="#dc2626", command=self._on_delete)
         self.del_btn.pack(side="right", padx=(3, 0))
 
         # Callbacks for add/edit/delete — set by app.py
@@ -50,6 +51,13 @@ class Sidebar(ctk.CTkFrame):
         self.store.subscribe(self._refresh_list)
         self._refresh_list()
 
+    def update_language(self):
+        self.title_label.configure(text=t("servers"))
+        self.search_entry.configure(placeholder_text=t("search"))
+        self.add_btn.configure(text=t("add"))
+        self.edit_btn.configure(text=t("edit"))
+        self.del_btn.configure(text=t("delete"))
+
     def _refresh_list(self):
         # Clear
         for widget in self.list_frame.winfo_children():