feat: Add material dimensions with typed properties

Implement TPH inheritance for material dimensions:
- MaterialShape enum with display names and parsing
- MaterialType enum (Steel, Aluminum, Stainless, etc.)
- MaterialDimensions base class with derived types per shape
- Auto-generate size strings from typed dimensions
- SortOrder field for numeric dimension sorting

Each shape has specific dimension properties:
- RoundBar: Diameter
- RoundTube: OuterDiameter, Wall
- FlatBar: Width, Thickness
- SquareBar/Tube: Size, Wall
- RectangularTube: Width, Height, Wall
- Angle: Leg1, Leg2, Thickness
- Channel: Height, Flange, Web
- IBeam: Height, WeightPerFoot
- Pipe: NominalSize, Wall, Schedule

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CutList.Web/Data/Entities/MaterialShape.cs

@@ -0,0 +1,89 @@
+namespace CutList.Web.Data.Entities;
+
+/// <summary>
+/// Enumeration of supported material shapes.
+/// </summary>
+public enum MaterialShape
+{
+    RoundBar,
+    RoundTube,
+    FlatBar,
+    SquareBar,
+    SquareTube,
+    RectangularTube,
+    Angle,
+    Channel,
+    IBeam,
+    Pipe
+}
+
+/// <summary>
+/// Extension methods for MaterialShape enum.
+/// </summary>
+public static class MaterialShapeExtensions
+{
+    /// <summary>
+    /// Gets the display name for a material shape.
+    /// </summary>
+    public static string GetDisplayName(this MaterialShape shape) => shape switch
+    {
+        MaterialShape.RoundBar => "Round Bar",
+        MaterialShape.RoundTube => "Round Tube",
+        MaterialShape.FlatBar => "Flat Bar",
+        MaterialShape.SquareBar => "Square Bar",
+        MaterialShape.SquareTube => "Square Tube",
+        MaterialShape.RectangularTube => "Rectangular Tube",
+        MaterialShape.Angle => "Angle",
+        MaterialShape.Channel => "Channel",
+        MaterialShape.IBeam => "I-Beam",
+        MaterialShape.Pipe => "Pipe",
+        _ => shape.ToString()
+    };
+
+    /// <summary>
+    /// Parses a display name or enum value string to a MaterialShape.
+    /// </summary>
+    public static MaterialShape? ParseShape(string? input)
+    {
+        if (string.IsNullOrWhiteSpace(input))
+            return null;
+
+        // Try exact enum parse first
+        if (Enum.TryParse<MaterialShape>(input, ignoreCase: true, out var result))
+            return result;
+
+        // Try display name matching
+        return input.Trim().ToLowerInvariant() switch
+        {
+            "round bar" => MaterialShape.RoundBar,
+            "round tube" => MaterialShape.RoundTube,
+            "flat bar" => MaterialShape.FlatBar,
+            "square bar" => MaterialShape.SquareBar,
+            "square tube" => MaterialShape.SquareTube,
+            "rectangular tube" or "rect tube" => MaterialShape.RectangularTube,
+            "angle" => MaterialShape.Angle,
+            "channel" => MaterialShape.Channel,
+            "i-beam" or "ibeam" or "i beam" => MaterialShape.IBeam,
+            "pipe" => MaterialShape.Pipe,
+            _ => null
+        };
+    }
+
+    /// <summary>
+    /// Gets the dimension field names used by a given shape.
+    /// </summary>
+    public static string[] GetDimensionFields(this MaterialShape shape) => shape switch
+    {
+        MaterialShape.RoundBar => new[] { "Diameter" },
+        MaterialShape.RoundTube => new[] { "OuterDiameter", "Wall" },
+        MaterialShape.FlatBar => new[] { "Width", "Thickness" },
+        MaterialShape.SquareBar => new[] { "Size" },
+        MaterialShape.SquareTube => new[] { "Size", "Wall" },
+        MaterialShape.RectangularTube => new[] { "Width", "Height", "Wall" },
+        MaterialShape.Angle => new[] { "Leg1", "Leg2", "Thickness" },
+        MaterialShape.Channel => new[] { "Height", "Flange", "Web" },
+        MaterialShape.IBeam => new[] { "Height", "WeightPerFoot" },
+        MaterialShape.Pipe => new[] { "NominalSize", "Wall", "Schedule" },
+        _ => Array.Empty<string>()
+    };
+}