Add configuration backup/restore with settings modal

Backend: GET /api/v1/system/backup bundles all 11 store JSON files into a
single downloadable backup with metadata envelope. POST /api/v1/system/restore
validates and writes stores atomically, then schedules a delayed server restart
via detached restart.ps1 subprocess.

Frontend: Settings modal (gear button in header) with Download Backup and
Restore from Backup buttons. Restore shows confirm dialog, uploads via
multipart FormData, then displays fullscreen restart overlay that polls
/health until the server comes back and reloads the page.

Locales: en, ru, zh translations for all settings.* keys.

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

server/src/wled_controller/api/routes/system.py

@@ -1,12 +1,17 @@
-"""System routes: health, version, displays, performance, ADB."""
+"""System routes: health, version, displays, performance, backup/restore, ADB."""
 
+import io
+import json
 import subprocess
 import sys
+import threading
 from datetime import datetime
+from pathlib import Path
 from typing import Optional
 
 import psutil
-from fastapi import APIRouter, Depends, HTTPException, Query
+from fastapi import APIRouter, Depends, File, HTTPException, Query, UploadFile
+from fastapi.responses import StreamingResponse
 from pydantic import BaseModel
 
 from wled_controller import __version__
@@ -19,10 +24,12 @@ from wled_controller.api.schemas.system import (
     HealthResponse,
     PerformanceResponse,
     ProcessListResponse,
+    RestoreResponse,
     VersionResponse,
 )
+from wled_controller.config import get_config
 from wled_controller.core.capture.screen_capture import get_available_displays
-from wled_controller.utils import get_logger
+from wled_controller.utils import atomic_write_json, get_logger
 
 logger = get_logger(__name__)
 
@@ -206,6 +213,141 @@ async def get_metrics_history(
     return manager.metrics_history.get_history()
 
 
+# ---------------------------------------------------------------------------
+# Configuration backup / restore
+# ---------------------------------------------------------------------------
+
+# Mapping: logical store name → StorageConfig attribute name
+STORE_MAP = {
+    "devices": "devices_file",
+    "capture_templates": "templates_file",
+    "postprocessing_templates": "postprocessing_templates_file",
+    "picture_sources": "picture_sources_file",
+    "picture_targets": "picture_targets_file",
+    "pattern_templates": "pattern_templates_file",
+    "color_strip_sources": "color_strip_sources_file",
+    "audio_sources": "audio_sources_file",
+    "audio_templates": "audio_templates_file",
+    "value_sources": "value_sources_file",
+    "profiles": "profiles_file",
+}
+
+_RESTART_SCRIPT = Path(__file__).resolve().parents[4] / "restart.ps1"
+
+
+def _schedule_restart() -> None:
+    """Spawn restart.ps1 after a short delay so the HTTP response completes."""
+
+    def _restart():
+        import time
+        time.sleep(1)
+        subprocess.Popen(
+            ["powershell", "-ExecutionPolicy", "Bypass", "-File", str(_RESTART_SCRIPT)],
+            creationflags=subprocess.DETACHED_PROCESS | subprocess.CREATE_NEW_PROCESS_GROUP,
+        )
+
+    threading.Thread(target=_restart, daemon=True).start()
+
+
+@router.get("/api/v1/system/backup", tags=["System"])
+def backup_config(_: AuthRequired):
+    """Download all configuration as a single JSON backup file."""
+    config = get_config()
+    stores = {}
+    for store_key, config_attr in STORE_MAP.items():
+        file_path = Path(getattr(config.storage, config_attr))
+        if file_path.exists():
+            with open(file_path, "r", encoding="utf-8") as f:
+                stores[store_key] = json.load(f)
+        else:
+            stores[store_key] = {}
+
+    backup = {
+        "meta": {
+            "format": "ledgrab-backup",
+            "format_version": 1,
+            "app_version": __version__,
+            "created_at": datetime.utcnow().isoformat() + "Z",
+            "store_count": len(stores),
+        },
+        "stores": stores,
+    }
+
+    content = json.dumps(backup, indent=2, ensure_ascii=False)
+    timestamp = datetime.utcnow().strftime("%Y-%m-%dT%H%M%S")
+    filename = f"ledgrab-backup-{timestamp}.json"
+
+    return StreamingResponse(
+        io.BytesIO(content.encode("utf-8")),
+        media_type="application/json",
+        headers={"Content-Disposition": f'attachment; filename="{filename}"'},
+    )
+
+
+@router.post("/api/v1/system/restore", response_model=RestoreResponse, tags=["System"])
+async def restore_config(
+    _: AuthRequired,
+    file: UploadFile = File(...),
+):
+    """Upload a backup file to restore all configuration. Triggers server restart."""
+    # Read and parse
+    try:
+        raw = await file.read()
+        if len(raw) > 10 * 1024 * 1024:  # 10 MB limit
+            raise HTTPException(status_code=400, detail="Backup file too large (max 10 MB)")
+        backup = json.loads(raw)
+    except json.JSONDecodeError as e:
+        raise HTTPException(status_code=400, detail=f"Invalid JSON file: {e}")
+
+    # Validate envelope
+    meta = backup.get("meta")
+    if not isinstance(meta, dict) or meta.get("format") != "ledgrab-backup":
+        raise HTTPException(status_code=400, detail="Not a valid LED Grab backup file")
+
+    fmt_version = meta.get("format_version", 0)
+    if fmt_version > 1:
+        raise HTTPException(
+            status_code=400,
+            detail=f"Backup format version {fmt_version} is not supported by this server version",
+        )
+
+    stores = backup.get("stores")
+    if not isinstance(stores, dict):
+        raise HTTPException(status_code=400, detail="Backup file missing 'stores' section")
+
+    known_keys = set(STORE_MAP.keys())
+    present_keys = known_keys & set(stores.keys())
+    if not present_keys:
+        raise HTTPException(status_code=400, detail="Backup contains no recognized store data")
+
+    for key in present_keys:
+        if not isinstance(stores[key], dict):
+            raise HTTPException(status_code=400, detail=f"Store '{key}' in backup is not a valid JSON object")
+
+    # Write store files atomically
+    config = get_config()
+    written = 0
+    for store_key, config_attr in STORE_MAP.items():
+        if store_key in stores:
+            file_path = Path(getattr(config.storage, config_attr))
+            atomic_write_json(file_path, stores[store_key])
+            written += 1
+            logger.info(f"Restored store: {store_key} -> {file_path}")
+
+    logger.info(f"Restore complete: {written}/{len(STORE_MAP)} stores written. Scheduling restart...")
+    _schedule_restart()
+
+    missing = known_keys - present_keys
+    return RestoreResponse(
+        status="restored",
+        stores_written=written,
+        stores_total=len(STORE_MAP),
+        missing_stores=sorted(missing) if missing else [],
+        restart_scheduled=True,
+        message=f"Restored {written} stores. Server restarting...",
+    )
+
+
 # ---------------------------------------------------------------------------
 # ADB helpers (for Android / scrcpy engine)
 # ---------------------------------------------------------------------------