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/Constants/VaultConstants.cs

@@ -9,4 +9,9 @@ public static class VaultConstants
     /// Vault name for storing audio tracks
     /// </summary>
     public const string Tracks = "tracks";
+
+    /// <summary>
+    /// Vault name for storing waveform loudness profile sidecars, keyed by track EntryKey.
+    /// </summary>
+    public const string WaveformProfiles = "waveform-profiles";
 }