Add CMS waveform pre-processing panel with backfill endpoints

GET api/track/waveform-status and POST api/track/{id}/waveform (ApiKey);
CmsTrackService methods; TrackPreProcessing page with per-row and
sequential bulk generation; nav links from TrackList and Index.

DeepDrftManager/Components/Pages/Index.razor

@@ -7,5 +7,19 @@
 
 <MudContainer MaxWidth="MaxWidth.Large" Class="mt-8">
     <MudText Typo="Typo.h3" GutterBottom="true">DeepDrft CMS</MudText>
-    <MudText Typo="Typo.body1">Administration panel — under construction.</MudText>
+    <MudText Typo="Typo.body1" Class="mb-4">Administration panel.</MudText>
+    <MudStack Row="true" Spacing="2">
+        <MudButton Variant="Variant.Filled"
+                   Color="Color.Primary"
+                   StartIcon="@Icons.Material.Filled.LibraryMusic"
+                   Href="/tracks">
+            Tracks
+        </MudButton>
+        <MudButton Variant="Variant.Outlined"
+                   Color="Color.Primary"
+                   StartIcon="@Icons.Material.Filled.GraphicEq"
+                   Href="/tracks/preprocessing">
+            Waveform Pre-Processing
+        </MudButton>
+    </MudStack>
 </MudContainer>