Add Shorts wizard and v4 video-style pipeline

Turn the Shorts tab into a step-by-step wizard and port
amigadb-short-fx-v4.sh: Video background style, auto/manual crop,
source fade-in, and blur/opacity/margin settings.

Models/AppSettings.cs

@@ -28,6 +28,16 @@ public sealed record AppSettings
     public string ShortsWebsite { get; init; } = "AMIGADB.NET";
     public string ShortsFontFile { get; init; } = "";
     public string ShortsBackgroundImage { get; init; } = "";
+    public string ShortsBackgroundVideo { get; init; } = "";
+    public string ShortsVideoBlur { get; init; } = "0";
+    public string ShortsVideoOpacity { get; init; } = "1.0";
+    public string ShortsSourceCropMode { get; init; } = "Auto";
+    public string ShortsCropLeft { get; init; } = "0";
+    public string ShortsCropRight { get; init; } = "0";
+    public string ShortsCropTop { get; init; } = "0";
+    public string ShortsCropBottom { get; init; } = "0";
+    public string ShortsSourceMarginX { get; init; } = "40";
+    public string ShortsSourceFadeIn { get; init; } = "1.5";
     public string ShortsCrf { get; init; } = "16";
     public string ShortsPreset { get; init; } = "slow";
 
@@ -68,6 +78,16 @@ public sealed record AppSettings
         ShortsWebsite = ShortsWebsite ?? "AMIGADB.NET",
         ShortsFontFile = ShortsFontFile ?? "",
         ShortsBackgroundImage = ShortsBackgroundImage ?? "",
+        ShortsBackgroundVideo = ShortsBackgroundVideo ?? "",
+        ShortsVideoBlur = string.IsNullOrWhiteSpace(ShortsVideoBlur) ? "0" : ShortsVideoBlur,
+        ShortsVideoOpacity = string.IsNullOrWhiteSpace(ShortsVideoOpacity) ? "1.0" : ShortsVideoOpacity,
+        ShortsSourceCropMode = string.IsNullOrWhiteSpace(ShortsSourceCropMode) ? "Auto" : ShortsSourceCropMode,
+        ShortsCropLeft = string.IsNullOrWhiteSpace(ShortsCropLeft) ? "0" : ShortsCropLeft,
+        ShortsCropRight = string.IsNullOrWhiteSpace(ShortsCropRight) ? "0" : ShortsCropRight,
+        ShortsCropTop = string.IsNullOrWhiteSpace(ShortsCropTop) ? "0" : ShortsCropTop,
+        ShortsCropBottom = string.IsNullOrWhiteSpace(ShortsCropBottom) ? "0" : ShortsCropBottom,
+        ShortsSourceMarginX = string.IsNullOrWhiteSpace(ShortsSourceMarginX) ? "40" : ShortsSourceMarginX,
+        ShortsSourceFadeIn = string.IsNullOrWhiteSpace(ShortsSourceFadeIn) ? "1.5" : ShortsSourceFadeIn,
         ShortsCrf = string.IsNullOrWhiteSpace(ShortsCrf) ? "16" : ShortsCrf,
         ShortsPreset = string.IsNullOrWhiteSpace(ShortsPreset) ? "slow" : ShortsPreset,
     };

Models/ShortSettings.cs

@@ -1,6 +1,6 @@
 namespace AmiReel.Models;
 
-/// <summary>Visual style applied to a YouTube Short. Mirrors the --style values of amigadb-short.sh.</summary>
+/// <summary>Visual style applied to a YouTube Short. Mirrors the --style values of amigadb-short-fx-v4.sh.</summary>
 public enum ShortStyle
 {
     Brand,
@@ -22,9 +22,17 @@ public enum ShortStyle
     Monitor,
     Split,
     Spectrum,
+    Video,
 }
 
-/// <summary>One YouTube Shorts render job's parameters (port of amigadb-short.sh's arguments).</summary>
+/// <summary>How the video style crops the Amiga source before overlaying it.</summary>
+public enum ShortSourceCropMode
+{
+    Auto,
+    Center,
+}
+
+/// <summary>One YouTube Shorts render job's parameters (port of amigadb-short-fx-v4.sh).</summary>
 public sealed record ShortSettings
 {
     public required string InputFile { get; init; }
@@ -39,6 +47,16 @@ public sealed record ShortSettings
     public required double DurationSeconds { get; init; }
     public required ShortStyle Style { get; init; }
     public string BackgroundImage { get; init; } = "";
+    public string BackgroundVideo { get; init; } = "";
+    public double VideoBlur { get; init; }
+    public double VideoOpacity { get; init; } = 1.0;
+    public ShortSourceCropMode SourceCropMode { get; init; } = ShortSourceCropMode.Auto;
+    public int CropLeft { get; init; }
+    public int CropRight { get; init; }
+    public int CropTop { get; init; }
+    public int CropBottom { get; init; }
+    public int SourceMarginX { get; init; } = 40;
+    public double SourceFadeInSeconds { get; init; } = 1.5;
     public required string FontFile { get; init; }
     public required string FfmpegPath { get; init; }
     public required string FfprobePath { get; init; }

Models/ShortWizard.cs

@@ -0,0 +1,63 @@
+namespace AmiReel.Models;
+
+/// <summary>One page of the Shorts create-wizard. Extra effect pages are inserted only when the style needs them.</summary>
+public enum ShortWizardStep
+{
+    Clip,
+    Effect,
+    StyleOptions,
+    Titles,
+    Encode,
+}
+
+/// <summary>Builds the Shorts wizard page list for a chosen visual style.</summary>
+public static class ShortWizard
+{
+    public static IReadOnlyList<ShortWizardStep> StepsFor(ShortStyle style)
+    {
+        List<ShortWizardStep> steps = [ShortWizardStep.Clip, ShortWizardStep.Effect];
+        if (NeedsStyleOptions(style))
+            steps.Add(ShortWizardStep.StyleOptions);
+        steps.Add(ShortWizardStep.Titles);
+        steps.Add(ShortWizardStep.Encode);
+        return steps;
+    }
+
+    public static bool NeedsStyleOptions(ShortStyle style) =>
+        style is ShortStyle.Brand or ShortStyle.Video;
+
+    public static string Title(ShortWizardStep step) => step switch
+    {
+        ShortWizardStep.Clip => "Source clip",
+        ShortWizardStep.Effect => "Visual effect",
+        ShortWizardStep.StyleOptions => "Effect settings",
+        ShortWizardStep.Titles => "Title card",
+        ShortWizardStep.Encode => "Encoding",
+        _ => "Short",
+    };
+
+    public static string Description(ShortStyle style) => style switch
+    {
+        ShortStyle.Brand => "Title-card background image with a framed source clip.",
+        ShortStyle.Pixel => "Pixelated backdrop with neon scan bars.",
+        ShortStyle.Mirror => "Reflected source strips above and below the clip.",
+        ShortStyle.Crop => "Full-frame vertical crop of the source.",
+        ShortStyle.Workbench => "Workbench-style window around the source.",
+        ShortStyle.Blur => "Blurred backdrop with a centered source.",
+        ShortStyle.Crt => "CRT curvature, scanlines, and a rolling highlight.",
+        ShortStyle.Copper => "Amiga copper bars behind the source.",
+        ShortStyle.Stars => "Twinkling star field behind a framed clip.",
+        ShortStyle.Grid => "Neon grid horizon behind the source.",
+        ShortStyle.Tiles => "Four-tile mirrored backdrop.",
+        ShortStyle.Scan => "Chunky scanlines and moving bars.",
+        ShortStyle.Starfield => "Fast-moving star streaks.",
+        ShortStyle.Plasma => "Demoscene plasma backdrop.",
+        ShortStyle.Rasterbars => "Classic raster bars above and below the clip.",
+        ShortStyle.Vhs => "Tape noise, chroma shift, and scanlines.",
+        ShortStyle.Monitor => "CRT monitor bezel around the source.",
+        ShortStyle.Split => "Split-band source strips around the main clip.",
+        ShortStyle.Spectrum => "Scrolling audio spectrum. The source video must have audio.",
+        ShortStyle.Video => "Looping background video with the Amiga clip overlaid.",
+        _ => "",
+    };
+}