Settings tabs, log overlay, external URL, Sources tree restructure, audio fixes

- Settings modal split into 3 tabs: General, Backup, MQTT
- Log viewer moved to full-screen overlay with compact toolbar
- External URL setting: API endpoints + UI for configuring server domain
  used in webhook/WS URLs instead of auto-detected local IP
- Sources tab tree restructured: Picture Source (Screen Capture/Static/
  Processed sub-groups), Color Strip, Audio, Utility
- TreeNav extended to support nested groups (3-level tree)
- Audio tab split into Sources and Templates sub-tabs
- Fix audio template test: device picker now filters by engine type
  (was showing WASAPI indices for sounddevice templates)
- Audio template test device picker disabled during active test
- Rename "Input Source" to "Source" in CSS test preview (en/ru/zh)
- Fix i18n: log filter/level items deferred to avoid stale t() calls

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -43,6 +43,8 @@ from wled_controller.api.schemas.system import (
     BackupListResponse,
     DisplayInfo,
     DisplayListResponse,
+    ExternalUrlRequest,
+    ExternalUrlResponse,
     GpuInfo,
     HealthResponse,
     LogLevelRequest,
@@ -763,6 +765,63 @@ async def update_mqtt_settings(_: AuthRequired, body: MQTTSettingsRequest):
     )
 
 
+# ---------------------------------------------------------------------------
+# External URL setting
+# ---------------------------------------------------------------------------
+
+_EXTERNAL_URL_FILE: Path | None = None
+
+
+def _get_external_url_path() -> Path:
+    global _EXTERNAL_URL_FILE
+    if _EXTERNAL_URL_FILE is None:
+        cfg = get_config()
+        data_dir = Path(cfg.storage.devices_file).parent
+        _EXTERNAL_URL_FILE = data_dir / "external_url.json"
+    return _EXTERNAL_URL_FILE
+
+
+def load_external_url() -> str:
+    """Load the external URL setting. Returns empty string if not set."""
+    path = _get_external_url_path()
+    if path.exists():
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                data = json.load(f)
+            return data.get("external_url", "")
+        except Exception:
+            pass
+    return ""
+
+
+def _save_external_url(url: str) -> None:
+    from wled_controller.utils import atomic_write_json
+    atomic_write_json(_get_external_url_path(), {"external_url": url})
+
+
+@router.get(
+    "/api/v1/system/external-url",
+    response_model=ExternalUrlResponse,
+    tags=["System"],
+)
+async def get_external_url(_: AuthRequired):
+    """Get the configured external base URL."""
+    return ExternalUrlResponse(external_url=load_external_url())
+
+
+@router.put(
+    "/api/v1/system/external-url",
+    response_model=ExternalUrlResponse,
+    tags=["System"],
+)
+async def update_external_url(_: AuthRequired, body: ExternalUrlRequest):
+    """Set the external base URL used in webhook URLs and other user-visible URLs."""
+    url = body.external_url.strip().rstrip("/")
+    _save_external_url(url)
+    logger.info("External URL updated: %s", url or "(cleared)")
+    return ExternalUrlResponse(external_url=url)
+
+
 # ---------------------------------------------------------------------------
 # Live log viewer WebSocket
 # ---------------------------------------------------------------------------