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/Migrations/20260205014058_FixMaterialShapeEnumValues.cs

@@ -0,0 +1,31 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace CutList.Web.Migrations
+{
+    /// <inheritdoc />
+    public partial class FixMaterialShapeEnumValues : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // Convert display names to enum names
+            migrationBuilder.Sql(@"
+                UPDATE Materials SET Shape = 'RoundBar' WHERE Shape = 'Round Bar';
+                UPDATE Materials SET Shape = 'RoundTube' WHERE Shape = 'Round Tube';
+                UPDATE Materials SET Shape = 'FlatBar' WHERE Shape = 'Flat Bar';
+                UPDATE Materials SET Shape = 'SquareBar' WHERE Shape = 'Square Bar';
+                UPDATE Materials SET Shape = 'SquareTube' WHERE Shape = 'Square Tube';
+                UPDATE Materials SET Shape = 'RectangularTube' WHERE Shape = 'Rectangular Tube';
+                UPDATE Materials SET Shape = 'IBeam' WHERE Shape = 'I-Beam';
+            ");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+
+        }
+    }
+}