feat: asset-based image/video sources, notification sounds, UI improvements

- Replace URL-based image_source/url fields with image_asset_id/video_asset_id
  on StaticImagePictureSource and VideoCaptureSource (clean break, no migration)
- Resolve asset IDs to file paths at runtime via AssetStore.get_file_path()
- Add EntitySelect asset pickers for image/video in stream editor modal
- Add notification sound configuration (global sound + per-app overrides)
- Unify per-app color and sound overrides into single "Per-App Overrides" section
- Persist notification history between server restarts
- Add asset management system (upload, edit, delete, soft-delete)
- Replace emoji buttons with SVG icons throughout UI
- Various backend improvements: SQLite stores, auth, backup, MQTT, webhooks

server/src/wled_controller/static/locales/en.json

@@ -593,22 +593,19 @@
     "streams.add.video": "Add Video Source",
     "streams.edit.video": "Edit Video Source",
     "picture_source.type.video": "Video",
-    "picture_source.type.video.desc": "Stream frames from video file, URL, or YouTube",
-    "picture_source.video.url": "Video URL:",
-    "picture_source.video.url.hint": "Local file path, HTTP URL, or YouTube URL",
-    "picture_source.video.url.placeholder": "https://example.com/video.mp4",
+    "picture_source.type.video.desc": "Stream frames from an uploaded video asset",
     "picture_source.video.loop": "Loop:",
     "picture_source.video.speed": "Playback Speed:",
     "picture_source.video.start_time": "Start Time (s):",
     "picture_source.video.end_time": "End Time (s):",
     "picture_source.video.resolution_limit": "Max Width (px):",
     "picture_source.video.resolution_limit.hint": "Downscale video at decode time for performance",
-    "streams.image_source": "Image Source:",
-    "streams.image_source.placeholder": "https://example.com/image.jpg or C:\\path\\to\\image.png",
-    "streams.image_source.hint": "Enter a URL (http/https) or local file path to an image",
-    "streams.validate_image.validating": "Validating...",
-    "streams.validate_image.valid": "Image accessible",
-    "streams.validate_image.invalid": "Image not accessible",
+    "streams.image_asset": "Image Asset:",
+    "streams.image_asset.select": "Select image asset…",
+    "streams.image_asset.search": "Search image assets…",
+    "streams.video_asset": "Video Asset:",
+    "streams.video_asset.select": "Select video asset…",
+    "streams.video_asset.search": "Search video assets…",
     "targets.title": "Targets",
     "targets.description": "Targets bridge color strip sources to output devices. Each target references a device and a color strip source.",
     "targets.subtab.wled": "LED",
@@ -1105,6 +1102,22 @@
     "color_strip.notification.app_colors.label": "Color Mappings:",
     "color_strip.notification.app_colors.hint": "Per-app color overrides. Each row maps an app name to a specific notification color.",
     "color_strip.notification.app_colors.add": "+ Add Mapping",
+    "color_strip.notification.app_overrides": "Per-App Overrides",
+    "color_strip.notification.app_overrides.label": "App Overrides:",
+    "color_strip.notification.app_overrides.hint": "Per-app overrides for color and sound. Each row can set a custom color, sound asset, and volume for a specific app.",
+    "color_strip.notification.app_overrides.add": "+ Add Override",
+    "color_strip.notification.app_overrides.app_placeholder": "App name",
+    "color_strip.notification.sound": "Sound",
+    "color_strip.notification.sound.asset": "Sound Asset:",
+    "color_strip.notification.sound.asset.hint": "Pick a sound asset to play when a notification fires. Leave empty for silent.",
+    "color_strip.notification.sound.none": "None (silent)",
+    "color_strip.notification.sound.search": "Search sounds…",
+    "color_strip.notification.sound.volume": "Volume:",
+    "color_strip.notification.sound.volume.hint": "Global volume for notification sounds (0–100%).",
+    "color_strip.notification.sound.app_sounds": "Per-App Sounds:",
+    "color_strip.notification.sound.app_sounds.hint": "Override sound and volume for specific apps. Empty sound = mute that app.",
+    "color_strip.notification.sound.app_sounds.add": "+ Add Override",
+    "color_strip.notification.sound.app_name_placeholder": "App name",
     "color_strip.notification.endpoint": "Webhook Endpoint:",
     "color_strip.notification.endpoint.hint": "Use this URL to trigger notifications from external systems. POST with optional JSON body: {\"app\": \"AppName\", \"color\": \"#FF0000\"}.",
     "color_strip.notification.save_first": "Save the source first to see the webhook endpoint URL.",
@@ -1963,9 +1976,35 @@
     "update.install_type.docker": "Docker",
     "update.install_type.dev": "Development",
 
-    "color_strip": {
-        "notification": {
-            "search_apps": "Search notification apps…"
-        }
-    }
+    "color_strip.notification.search_apps": "Search notification apps…",
+
+    "asset.group.title": "Assets",
+    "asset.upload": "Upload Asset",
+    "asset.edit": "Edit Asset",
+    "asset.name": "Name:",
+    "asset.name.hint": "Display name for this asset.",
+    "asset.description": "Description:",
+    "asset.description.hint": "Optional description for this asset.",
+    "asset.file": "File:",
+    "asset.file.hint": "Select a file to upload (sound, image, video, or other).",
+    "asset.drop_or_browse": "Drop file here or click to browse",
+    "asset.uploaded": "Asset uploaded",
+    "asset.updated": "Asset updated",
+    "asset.deleted": "Asset deleted",
+    "asset.confirm_delete": "Delete this asset?",
+    "asset.error.name_required": "Name is required",
+    "asset.error.no_file": "Please select a file to upload",
+    "asset.error.delete_failed": "Failed to delete asset",
+    "asset.play": "Play",
+    "asset.download": "Download",
+    "asset.prebuilt": "Prebuilt",
+    "asset.prebuilt_restored": "{count} prebuilt asset(s) restored",
+    "asset.prebuilt_none_to_restore": "All prebuilt assets are already available",
+    "asset.restore_prebuilt": "Restore Prebuilt Sounds",
+    "asset.type.sound": "Sound",
+    "asset.type.image": "Image",
+    "asset.type.video": "Video",
+    "asset.type.other": "Other",
+    "streams.group.assets": "Assets",
+    "section.empty.assets": "No assets yet. Click + to upload one."
 }