feat: migrate storage from JSON files to SQLite

Replace 22 individual JSON store files with a single SQLite database
(data/ledgrab.db). All entity stores now use BaseSqliteStore backed by
SQLite with WAL mode, write-through caching, and thread-safe access.

- Add Database class with SQLite backup/restore API
- Add BaseSqliteStore as drop-in replacement for BaseJsonStore
- Convert all 16 entity stores to SQLite
- Move global settings (MQTT, external URL, auto-backup) to SQLite
  settings table
- Replace JSON backup/restore with SQLite snapshot backups (.db files)
- Remove partial export/import feature (backend + frontend)
- Update demo seed to write directly to SQLite
- Add "Backup Now" button to settings UI
- Remove StorageConfig file path fields (single database_file remains)

server/src/wled_controller/main.py

@@ -41,7 +41,7 @@ from wled_controller.core.mqtt.mqtt_service import MQTTService
 from wled_controller.core.devices.mqtt_client import set_mqtt_service
 from wled_controller.core.backup.auto_backup import AutoBackupEngine
 from wled_controller.core.processing.os_notification_listener import OsNotificationListener
-from wled_controller.api.routes.system import STORE_MAP
+from wled_controller.storage.database import Database
 from wled_controller.utils import setup_logging, get_logger, install_broadcast_handler
 
 # Initialize logging
@@ -52,29 +52,32 @@ logger = get_logger(__name__)
 # Get configuration
 config = get_config()
 
-# Seed demo data before stores are loaded (first-run only)
+# Initialize SQLite database
+db = Database(config.storage.database_file)
+
+# Seed demo data after DB is ready (first-run only)
 if config.demo:
     from wled_controller.core.demo_seed import seed_demo_data
-    seed_demo_data(config.storage)
+    seed_demo_data(db)
 
 # Initialize storage and processing
-device_store = DeviceStore(config.storage.devices_file)
-template_store = TemplateStore(config.storage.templates_file)
-pp_template_store = PostprocessingTemplateStore(config.storage.postprocessing_templates_file)
-picture_source_store = PictureSourceStore(config.storage.picture_sources_file)
-output_target_store = OutputTargetStore(config.storage.output_targets_file)
-pattern_template_store = PatternTemplateStore(config.storage.pattern_templates_file)
-color_strip_store = ColorStripStore(config.storage.color_strip_sources_file)
-audio_source_store = AudioSourceStore(config.storage.audio_sources_file)
-audio_template_store = AudioTemplateStore(config.storage.audio_templates_file)
-value_source_store = ValueSourceStore(config.storage.value_sources_file)
-automation_store = AutomationStore(config.storage.automations_file)
-scene_preset_store = ScenePresetStore(config.storage.scene_presets_file)
-sync_clock_store = SyncClockStore(config.storage.sync_clocks_file)
-cspt_store = ColorStripProcessingTemplateStore(config.storage.color_strip_processing_templates_file)
-gradient_store = GradientStore(config.storage.gradients_file)
+device_store = DeviceStore(db)
+template_store = TemplateStore(db)
+pp_template_store = PostprocessingTemplateStore(db)
+picture_source_store = PictureSourceStore(db)
+output_target_store = OutputTargetStore(db)
+pattern_template_store = PatternTemplateStore(db)
+color_strip_store = ColorStripStore(db)
+audio_source_store = AudioSourceStore(db)
+audio_template_store = AudioTemplateStore(db)
+value_source_store = ValueSourceStore(db)
+automation_store = AutomationStore(db)
+scene_preset_store = ScenePresetStore(db)
+sync_clock_store = SyncClockStore(db)
+cspt_store = ColorStripProcessingTemplateStore(db)
+gradient_store = GradientStore(db)
 gradient_store.migrate_palette_references(color_strip_store)
-weather_source_store = WeatherSourceStore(config.storage.weather_sources_file)
+weather_source_store = WeatherSourceStore(db)
 sync_clock_manager = SyncClockManager(sync_clock_store)
 weather_manager = WeatherManager(weather_source_store)
 
@@ -156,34 +159,18 @@ async def lifespan(app: FastAPI):
         device_store=device_store,
     )
 
-    # Create auto-backup engine — derive paths from storage config so that
+    # Create auto-backup engine — derive paths from database location so that
     # demo mode auto-backups go to data/demo/ instead of data/.
-    _data_dir = Path(config.storage.devices_file).parent
+    _data_dir = Path(config.storage.database_file).parent
     auto_backup_engine = AutoBackupEngine(
-        settings_path=_data_dir / "auto_backup_settings.json",
         backup_dir=_data_dir / "backups",
-        store_map=STORE_MAP,
-        storage_config=config.storage,
+        db=db,
     )
 
-    # Verify STORE_MAP covers all StorageConfig file fields.
-    # Catches missed additions early (at startup) rather than silently
-    # excluding new stores from backups.
-    storage_attrs = {
-        attr for attr in config.storage.model_fields
-        if attr.endswith("_file")
-    }
-    mapped_attrs = set(STORE_MAP.values())
-    unmapped = storage_attrs - mapped_attrs
-    if unmapped:
-        logger.warning(
-            f"StorageConfig fields not in STORE_MAP (missing from backups): "
-            f"{sorted(unmapped)}"
-        )
-
     # Initialize API dependencies
     init_dependencies(
         device_store, template_store, processor_manager,
+        database=db,
         pp_template_store=pp_template_store,
         pattern_template_store=pattern_template_store,
         picture_source_store=picture_source_store,