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/tabs/info_tab.py

@@ -3,9 +3,22 @@ Info tab — display server details, edit button.
 """
 
 import customtkinter as ctk
+from core.i18n import t
 
 
 class InfoTab(ctk.CTkFrame):
+    # Map field keys to i18n keys
+    _FIELD_KEYS = ["alias", "ip", "port", "user", "type", "notes", "status"]
+    _FIELD_I18N = {
+        "alias": "info_alias",
+        "ip": "info_ip",
+        "port": "info_port",
+        "user": "info_user",
+        "type": "info_type",
+        "notes": "info_notes",
+        "status": "info_status",
+    }
+
     def __init__(self, master, store, edit_callback=None):
         super().__init__(master, fg_color="transparent")
         self.store = store
@@ -13,7 +26,7 @@ class InfoTab(ctk.CTkFrame):
         self._current_alias: str | None = None
 
         # Header
-        self.header = ctk.CTkLabel(self, text="No server selected", font=ctk.CTkFont(size=20, weight="bold"))
+        self.header = ctk.CTkLabel(self, text=t("no_server_selected_info"), font=ctk.CTkFont(size=20, weight="bold"))
         self.header.pack(padx=20, pady=(20, 10))
 
         # Info card
@@ -21,17 +34,20 @@ class InfoTab(ctk.CTkFrame):
         self.card.pack(fill="x", padx=20, pady=10)
 
         self._fields: dict[str, ctk.CTkLabel] = {}
-        for label in ["Alias", "IP", "Port", "User", "Type", "Notes", "Status"]:
+        self._field_labels: dict[str, ctk.CTkLabel] = {}
+        for key in self._FIELD_KEYS:
             row = ctk.CTkFrame(self.card, fg_color="transparent")
             row.pack(fill="x", padx=15, pady=4)
-            ctk.CTkLabel(row, text=f"{label}:", width=80, anchor="w",
-                        font=ctk.CTkFont(size=12), text_color="#9ca3af").pack(side="left")
+            label = ctk.CTkLabel(row, text=t(self._FIELD_I18N[key]), width=80, anchor="w",
+                        font=ctk.CTkFont(size=12), text_color="#9ca3af")
+            label.pack(side="left")
             val = ctk.CTkLabel(row, text="-", anchor="w", font=ctk.CTkFont(size=13))
             val.pack(side="left", fill="x", expand=True)
-            self._fields[label] = val
+            self._field_labels[key] = label
+            self._fields[key] = val
 
         # Edit button
-        self.edit_btn = ctk.CTkButton(self, text="Edit Server", command=self._on_edit)
+        self.edit_btn = ctk.CTkButton(self, text=t("edit_server_btn"), command=self._on_edit)
         self.edit_btn.pack(pady=15)
 
     def set_server(self, alias: str | None):
@@ -40,7 +56,7 @@ class InfoTab(ctk.CTkFrame):
 
     def refresh(self):
         if not self._current_alias:
-            self.header.configure(text="No server selected")
+            self.header.configure(text=t("no_server_selected_info"))
             for v in self._fields.values():
                 v.configure(text="-")
             return
@@ -50,16 +66,16 @@ class InfoTab(ctk.CTkFrame):
             return
 
         self.header.configure(text=server["alias"])
-        self._fields["Alias"].configure(text=server.get("alias", "-"))
-        self._fields["IP"].configure(text=server.get("ip", "-"))
-        self._fields["Port"].configure(text=str(server.get("port", 22)))
-        self._fields["User"].configure(text=server.get("user", "root"))
-        self._fields["Type"].configure(text=server.get("type", "ssh").upper())
-        self._fields["Notes"].configure(text=server.get("notes", "-") or "-")
+        self._fields["alias"].configure(text=server.get("alias", "-"))
+        self._fields["ip"].configure(text=server.get("ip", "-"))
+        self._fields["port"].configure(text=str(server.get("port", 22)))
+        self._fields["user"].configure(text=server.get("user", "root"))
+        self._fields["type"].configure(text=server.get("type", "ssh").upper())
+        self._fields["notes"].configure(text=server.get("notes", "-") or "-")
 
         status = self.store.get_status(self._current_alias)
         color = {"online": "#22c55e", "offline": "#ef4444"}.get(status, "#9ca3af")
-        self._fields["Status"].configure(text=status.upper(), text_color=color)
+        self._fields["status"].configure(text=status.upper(), text_color=color)
 
     def _on_edit(self):
         if self.edit_callback and self._current_alias: