Update SPPreview version and enhance OkMatch<T> handling

Updated the SPPreview version in Directory.Build.props from
-preview-4.8 to -preview-4.9. Added a new using directive for
RoyalCode.SmartProblems.Entities in OkMatch'1.cs. Introduced
an implicit conversion operator and a new constructor in the
OkMatch<T> class to handle FindResult<T> objects more
effectively, providing specific logic for "not found" cases.

Author: eglauko

src/Directory.Build.props

@@ -10,7 +10,7 @@
 	</PropertyGroup>
 	<PropertyGroup>
 		<SPVer>1.0.0</SPVer>
-		<SPPreview>-preview-4.8</SPPreview>
+		<SPPreview>-preview-4.9</SPPreview>
 	</PropertyGroup>
 	<PropertyGroup>
 		<FluentValidationVer>12.0.0</FluentValidationVer>

src/RoyalCode.SmartProblems.ApiResults/HttpResults/OkMatch'1.cs

@@ -2,6 +2,7 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.HttpResults;
 using Microsoft.AspNetCore.Http.Metadata;
+using RoyalCode.SmartProblems.Entities;
 using RoyalCode.SmartProblems.Metadata;
 using System.Net.Mime;
 using System.Reflection;
@@ -28,6 +29,13 @@ public sealed class OkMatch<T> : IResult, INestedHttpResult, IEndpointMetadataPr
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static implicit operator OkMatch<T>(Result<T> result) => new(result);
 
+    /// <summary>
+    /// Creates a new <see cref="OkMatch{T}"/> for the <see cref="Result{TValue}"/>.
+    /// </summary>
+    /// <param name="result"></param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator OkMatch<T>(FindResult<T> result) => new(result);
+
     /// <summary>
     /// Creates a new <see cref="OkMatch{T}"/> for the <see cref="Ok{TValue}"/>.
     /// </summary>
@@ -74,6 +82,17 @@ public OkMatch(Result<T> result)
             static error => new MatchErrorResult(error));
     }
 
+    /// <summary>
+    /// Creates a new <see cref="IResult"/> for the <see cref="FindResult{TEntity}"/> match.
+    /// </summary>
+    /// <param name="result">The <see cref="FindResult{TEntity}"/> to be converted.</param>
+    public OkMatch(FindResult<T> result)
+    {
+        Result = result.NotFound(out var problem) 
+            ? new MatchErrorResult(problem)
+            : TypedResults.Ok(result.Entity);
+    }
+
     /// <summary>
     /// Creates a new <see cref="OkMatch{T}"/> for the <see cref="Ok{TValue}"/> match.
     /// </summary>