Add audio-reactive color strip sources, improve delete error messages

Add new "audio" color strip source type with three visualization modes
(spectrum analyzer, beat pulse, VU meter) supporting WASAPI loopback and
microphone input via PyAudioWPatch. Includes shared audio capture with
ref counting, real-time FFT spectrum analysis, and beat detection.

Improve all referential integrity 409 error messages across delete
endpoints to include specific names of referencing entities instead of
generic "one or more" messages.

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

server/src/wled_controller/api/__init__.py

@@ -10,6 +10,7 @@ from .routes.picture_sources import router as picture_sources_router
 from .routes.pattern_templates import router as pattern_templates_router
 from .routes.picture_targets import router as picture_targets_router
 from .routes.color_strip_sources import router as color_strip_sources_router
+from .routes.audio import router as audio_router
 from .routes.profiles import router as profiles_router
 
 router = APIRouter()
@@ -20,6 +21,7 @@ router.include_router(postprocessing_router)
 router.include_router(pattern_templates_router)
 router.include_router(picture_sources_router)
 router.include_router(color_strip_sources_router)
+router.include_router(audio_router)
 router.include_router(picture_targets_router)
 router.include_router(profiles_router)