Add server-side waveform loudness profiling on track upload

ILoudnessAlgorithm strategy (RmsLoudnessAlgorithm first impl), WaveformProfileService
stores quantized byte[] sidecar in new MediaFileVault (profiles vault), wired into
UnifiedTrackService.UploadAsync; failure is logged and swallowed. WaveformProfileDto
and WaveformProfileOptions in shared projects.

DeepDrftContent/Processors/WaveformProfileOptions.cs

@@ -0,0 +1,11 @@
+namespace DeepDrftContent.Processors;
+
+/// <summary>
+/// Configuration for waveform loudness profiling. <see cref="BucketCount"/> is the stored
+/// resolution — the number of loudness buckets computed and persisted per track, which is also
+/// the bar count the frontend WaveformSeeker renders.
+/// </summary>
+public class WaveformProfileOptions
+{
+    public int BucketCount { get; set; } = 512;
+}