feat: import/export for config and backups

- Add export_config/import_config/export_backup/import_backup to ServerStore
- Add 4 buttons row in Setup tab UI with file dialogs
- Add i18n keys for EN/RU/ZH (16 keys each)

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

core/server_store.py

@@ -237,6 +237,80 @@ class ServerStore:
         self._notify()
         log.info(f"Restored from: {filename}")
 
+    # ── Import / Export ──────────────────────────────
+
+    def export_config(self, dest_path: str) -> str:
+        text = json.dumps(self._data, indent=2, ensure_ascii=False)
+        with open(dest_path, "w", encoding="utf-8") as f:
+            f.write(text)
+        log.info(f"Config exported to: {dest_path}")
+        return dest_path
+
+    def import_config(self, src_path: str):
+        if not os.path.exists(src_path):
+            raise FileNotFoundError(f"File not found: {src_path}")
+        with open(src_path, "rb") as f:
+            raw = f.read()
+        try:
+            if is_encrypted(raw):
+                text = decrypt(raw)
+                data = json.loads(text)
+            else:
+                data = json.loads(raw.decode("utf-8"))
+        except Exception as e:
+            raise ValueError(f"Invalid config file: {e}")
+        if not isinstance(data, dict) or not isinstance(data.get("servers"), list):
+            raise ValueError("Invalid config structure: missing 'servers' list")
+        self._data = data
+        self._save()
+        self._notify()
+        log.info(f"Config imported from: {src_path}")
+
+    def export_backup(self, filename: str, dest_path: str) -> str:
+        src = os.path.join(BACKUP_DIR, filename)
+        if not os.path.exists(src):
+            raise FileNotFoundError(f"Backup not found: {filename}")
+        with open(src, "rb") as f:
+            raw = f.read()
+        if is_encrypted(raw):
+            text = decrypt(raw)
+            data = json.loads(text)
+        else:
+            data = json.loads(raw.decode("utf-8"))
+        with open(dest_path, "w", encoding="utf-8") as f:
+            json.dump(data, indent=2, ensure_ascii=False, fp=f)
+        log.info(f"Backup exported to: {dest_path}")
+        return dest_path
+
+    def import_backup(self, src_path: str) -> str:
+        if not os.path.exists(src_path):
+            raise FileNotFoundError(f"File not found: {src_path}")
+        with open(src_path, "rb") as f:
+            raw = f.read()
+        try:
+            if is_encrypted(raw):
+                text = decrypt(raw)
+                data = json.loads(text)
+            else:
+                data = json.loads(raw.decode("utf-8"))
+        except Exception as e:
+            raise ValueError(f"Invalid backup file: {e}")
+        if not isinstance(data, dict) or not isinstance(data.get("servers"), list):
+            raise ValueError("Invalid backup structure: missing 'servers' list")
+        name = os.path.basename(src_path)
+        dest = os.path.join(BACKUP_DIR, name)
+        if os.path.exists(dest):
+            stem, ext = os.path.splitext(name)
+            suffix = datetime.now().strftime("_%H%M%S")
+            name = stem + suffix + ext
+            dest = os.path.join(BACKUP_DIR, name)
+        os.makedirs(BACKUP_DIR, exist_ok=True)
+        encrypted = encrypt(json.dumps(data, indent=2, ensure_ascii=False))
+        with open(dest, "wb") as f:
+            f.write(encrypted)
+        log.info(f"Backup imported: {name}")
+        return name
+
     # ── Observer ──────────────────────────────────────
 
     def _notify(self):