feat: add Vietnamese localization to GUI

Introduces a two-language (EN/VI) i18n system with hot-swap support.
All ~160 user-facing strings are centralised in gui/locales.py; views
retranslate in-place on language switch without restarting the app.

- gui/locales.py: new file — _EN/_VI dicts, t() lookup, set_language(),
  get_language(); assert guard ensures EN/VI key parity
- gui/app.py: switch_language(), _apply_startup_language(),
  _save_language_pref(), _rebuild_nav_labels(); language stored in
  config.json under ui.language; pipeline step headers and run_tool
  status lines translated
- gui/views/settings.py: Language dropdown card (English / Tiếng Việt)
- gui/views/dashboard.py: all strings via t(); static header widgets
  stored and retranslated in refresh()
- gui/views/mods.py: all strings via t(); _STATUS dict built at call
  time so server status labels update on language switch
- gui/views/tools.py: all strings via _translatable registry; tab names
  and segmented-button values kept in English (CTkTabview constraint)
- gui/views/logs.py: title + Copy/Clear buttons stored, retranslated
- gui/wizard.py: all 3 pages fully translated
- docs/huong-dan-su-dung.md: full Vietnamese user guide
- CLAUDE.md: documents localization architecture and constraints

gui/views/logs.py

@@ -5,6 +5,7 @@ from typing import TYPE_CHECKING
 import customtkinter as ctk
 
 from gui._constants import COLOR_ERROR
+from gui.locales import t
 from gui.views.base import BaseView
 
 if TYPE_CHECKING:
@@ -27,16 +28,19 @@ class LogsView(BaseView):
         # ── Header ────────────────────────────────────────────────────────────
         hdr = ctk.CTkFrame(self, fg_color="transparent")
         hdr.grid(row=0, column=0, sticky="ew", padx=24, pady=(20, 8))
-        ctk.CTkLabel(hdr, text="Logs",
-                     font=ctk.CTkFont(size=22, weight="bold")).pack(side="left")
+        self._title_lbl = ctk.CTkLabel(hdr, text=t("logs.title"),
+                                       font=ctk.CTkFont(size=22, weight="bold"))
+        self._title_lbl.pack(side="left")
 
         btn_row = ctk.CTkFrame(hdr, fg_color="transparent")
         btn_row.pack(side="right")
-        ctk.CTkButton(btn_row, text="Copy", width=72,
-                      command=self._copy).pack(side="left", padx=4)
-        ctk.CTkButton(btn_row, text="Clear", width=72,
-                      fg_color=COLOR_ERROR, hover_color="#c62828",
-                      command=self._clear).pack(side="left")
+        self._copy_btn = ctk.CTkButton(btn_row, text=t("logs.copy_btn"), width=72,
+                                       command=self._copy)
+        self._copy_btn.pack(side="left", padx=4)
+        self._clear_btn = ctk.CTkButton(btn_row, text=t("logs.clear_btn"), width=72,
+                                        fg_color=COLOR_ERROR, hover_color="#c62828",
+                                        command=self._clear)
+        self._clear_btn.pack(side="left")
 
         # ── Log textbox (persistent) ──────────────────────────────────────────
         self._log_box = ctk.CTkTextbox(
@@ -44,6 +48,12 @@ class LogsView(BaseView):
             font=ctk.CTkFont(family="Consolas", size=12))
         self._log_box.grid(row=1, column=0, sticky="nsew", padx=24, pady=(0, 12))
 
+    def refresh(self) -> None:
+        # Retranslate header widgets (log content intentionally preserved)
+        self._title_lbl.configure(text=t("logs.title"))
+        self._copy_btn.configure(text=t("logs.copy_btn"))
+        self._clear_btn.configure(text=t("logs.clear_btn"))
+
     def append(self, text: str) -> None:
         """Thread-safe-ish: called from the app's after() poll loop (main thread)."""
         try: