fix(media): check the file type before the size cap on media upload

AddMedia sized a file before validating its type, and ValidateSize's Unknown
arm returned the video message, so a 150 MB .exe sent as
application/octet-stream was rejected as FileTooLarge with "Videos must be
100 MB or smaller." EnsureAllowed now runs first, so an unsupported file always
reports UnsupportedMediaType, and the Unknown arm uses a type-neutral message.
The oversize controller tests now use real file headers so they pass the type
check before reaching the size cap.

Api.SeaHavenIndustries.Tests/WorkOrderMediaControllerTests.cs

@@ -56,14 +56,11 @@ public class WorkOrderMediaControllerTests
     [Fact]
     public async Task AddMedia_VideoOverHundredMegabytes_ReturnsStableUnprocessableEntity()
     {
-        var file = new Mock<IFormFile>();
+        var file = OversizeFile(100_000_001, "clip.mp4", "video/mp4", FtypHeader);
-        file.SetupGet(candidate => candidate.Length).Returns(100_000_001);
-        file.SetupGet(candidate => candidate.FileName).Returns("clip.mp4");
-        file.SetupGet(candidate => candidate.ContentType).Returns("video/mp4");
         var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
         var controller = CreateController(storage: storage);
 
-        var result = await controller.AddMedia(1, null, file.Object, CancellationToken.None);
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
 
         var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
         var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
@@ -75,14 +72,11 @@ public class WorkOrderMediaControllerTests
     [Fact]
     public async Task AddMedia_PhotoOverTenMegabytes_ReturnsStableUnprocessableEntity()
     {
-        var file = new Mock<IFormFile>();
+        var file = OversizeFile(10_000_001, "photo.jpg", "image/jpeg", JpegHeader);
-        file.SetupGet(candidate => candidate.Length).Returns(10_000_001);
-        file.SetupGet(candidate => candidate.FileName).Returns("photo.jpg");
-        file.SetupGet(candidate => candidate.ContentType).Returns("image/jpeg");
         var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
         var controller = CreateController(storage: storage);
 
-        var result = await controller.AddMedia(1, null, file.Object, CancellationToken.None);
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
 
         var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
         var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
@@ -96,14 +90,11 @@ public class WorkOrderMediaControllerTests
     {
         // A .jpg with a foreign video type resolves to image/jpeg for validation, so it must
         // also be sized as a photo, not given the 100 MB video allowance.
-        var file = new Mock<IFormFile>();
+        var file = OversizeFile(60_000_000, "photo.jpg", "video/3gpp", JpegHeader);
-        file.SetupGet(candidate => candidate.Length).Returns(60_000_000);
-        file.SetupGet(candidate => candidate.FileName).Returns("photo.jpg");
-        file.SetupGet(candidate => candidate.ContentType).Returns("video/3gpp");
         var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
         var controller = CreateController(storage: storage);
 
-        var result = await controller.AddMedia(1, null, file.Object, CancellationToken.None);
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
 
         var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
         var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
@@ -115,14 +106,11 @@ public class WorkOrderMediaControllerTests
     [Fact]
     public async Task AddMedia_DocumentOverFiftyMegabytes_ReturnsStableUnprocessableEntity()
     {
-        var file = new Mock<IFormFile>();
+        var file = OversizeFile(50_000_001, "report.pdf", "application/pdf", PdfHeader);
-        file.SetupGet(candidate => candidate.Length).Returns(50_000_001);
-        file.SetupGet(candidate => candidate.FileName).Returns("report.pdf");
-        file.SetupGet(candidate => candidate.ContentType).Returns("application/pdf");
         var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
         var controller = CreateController(storage: storage);
 
-        var result = await controller.AddMedia(1, WorkOrderMediaCategory.Extra, file.Object, CancellationToken.None);
+        var result = await controller.AddMedia(1, WorkOrderMediaCategory.Extra, file, CancellationToken.None);
 
         var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
         var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
@@ -131,6 +119,48 @@ public class WorkOrderMediaControllerTests
         storage.VerifyNoOtherCalls();
     }
 
+    [Fact]
+    public async Task AddMedia_OversizeUnsupportedType_ReportsUnsupportedTypeNotOversizeVideo()
+    {
+        var file = OversizeFile(150_000_000, "payload.exe", "application/octet-stream", [0x4D, 0x5A]);
+        var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
+        var controller = CreateController(storage: storage);
+
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
+
+        var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
+        var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
+        Assert.Equal("UnsupportedMediaType", error.Code);
+        storage.VerifyNoOtherCalls();
+    }
+
+    [Fact]
+    public void ValidateSize_OversizeUnknownKind_UsesTypeNeutralMessage()
+    {
+        Assert.Equal(
+            "Files must be 100 MB or smaller.",
+            WorkOrderMediaContract.ValidateSize(150_000_000, WorkOrderMediaContract.UploadKind.Unknown));
+    }
+
+    private static readonly byte[] FtypHeader = [0, 0, 0, 0x18, (byte)'f', (byte)'t', (byte)'y', (byte)'p', (byte)'i', (byte)'s', (byte)'o', (byte)'m'];
+    private static readonly byte[] JpegHeader = [0xFF, 0xD8, 0xFF, 0xE0];
+    private static readonly byte[] PdfHeader = [0x25, 0x50, 0x44, 0x46, 0x2D];
+
+    /// <summary>
+    /// A file that reports <paramref name="length"/> bytes but only backs the 512-byte header the
+    /// type rules read, so oversize cases run through real signature validation cheaply.
+    /// </summary>
+    private static FormFile OversizeFile(long length, string fileName, string contentType, byte[] header)
+    {
+        var bytes = new byte[512];
+        header.CopyTo(bytes, 0);
+        return new FormFile(new MemoryStream(bytes), 0, length, "file", fileName)
+        {
+            Headers = new HeaderDictionary(),
+            ContentType = contentType
+        };
+    }
+
     private static FormFile VideoFormFile(int size, string fileName, string contentType)
     {
         var bytes = new byte[size];

Api.SeaHavenIndustries/Controllers/WorkOrderMediaController.cs

@@ -88,6 +88,10 @@ namespace Api.SeaHavenIndustries.Controllers
             string? fileUrl = null;
             try
             {
+                // Type first, so an unsupported file always reports UnsupportedMediaType instead
+                // of being sized under a kind it does not have.
+                WorkOrderMediaFileRules.EnsureAllowed(file, category);
+
                 // SH-116 contract: per-kind caps (photos 10 MB, videos 100 MB, documents 50 MB).
                 // Classify by the same resolved type EnsureAllowed validates against.
                 var sizeMessage = WorkOrderMediaContract.ValidateSize(
@@ -97,7 +101,6 @@ namespace Api.SeaHavenIndustries.Controllers
                     throw new WorkOrderBoardValidationException("FileTooLarge", sizeMessage);
                 }
 
-                WorkOrderMediaFileRules.EnsureAllowed(file, category);
                 if (WorkOrderMediaContract.ResolveKind(
                         WorkOrderMediaFileRules.ResolveUploadContentType(file), file.FileName)
                     == WorkOrderMediaContract.UploadKind.Video)

SeaHaven.Services/Helpers/WorkOrderMediaContract.cs

@@ -138,7 +138,7 @@ namespace SeaHaven.Services.Helpers
                 UploadKind.Document when length > MaxDocumentBytes =>
                     "Documents must be 50 MB or smaller.",
                 UploadKind.Unknown when length > MaxVideoBytes =>
-                    "Videos must be 100 MB or smaller.",
+                    "Files must be 100 MB or smaller.",
                 _ => null
             };
         }