Fixed: Stack overflow in SizeSuffix and overflow in Fluent.Round

Calling NumberExtensions.SizeSuffix(long.MinValue) recurses forever:
-bytes overflows back to long.MinValue (no representable positive twin
in Int64), the `bytes < 0` branch always re-fires, and the .NET runtime
kills the process with an uncatchable StackOverflowException.

This actually fires in the wild — an indexer returned a release whose
parsed size landed at MinValue, RssSyncService -> DownloadDecisionMaker
-> AcceptableSizeSpecification called SizeSuffix on it, and Radarr was
killed mid-RSS-sync. Also explains the "unable to load results for this
movie search" UI symptom that collateral interactive searches hit when
the process died mid-flight.

Fluent.Round had a related but separate Convert.ToInt64 overflow on
extreme values (Math.Floor of very negative `number` produced an
out-of-range double); guard with Math.Ceiling for negatives.

This is a port of Sonarr/Sonarr@be4a564456
(by @mynameisbogdan), as suggested by them on the Radarr issue.

Closes #11404

src/NzbDrone.Common.Test/ExtensionTests/NumberExtensionFixture.cs

@@ -17,6 +17,8 @@ public class NumberExtensionFixture
         [TestCase(-1000000, "-976.6 KB")]
         [TestCase(-377487360, "-360.0 MB")]
         [TestCase(-1255864686, "-1.2 GB")]
+        [TestCase(long.MinValue, "-8.0 EB")]
+        [TestCase(long.MaxValue, "8.0 EB")]
         public void should_calculate_string_correctly(long bytes, string expected)
         {
             bytes.SizeSuffix().Should().Be(expected);

src/NzbDrone.Common/Extensions/NumberExtensions.cs

@@ -11,16 +11,21 @@ public static string SizeSuffix(this long bytes)
         {
             const int bytesInKb = 1024;
 
-            if (bytes < 0)
-            {
-                return "-" + SizeSuffix(-bytes);
-            }
-
             if (bytes == 0)
             {
                 return "0 B";
             }
 
+            if (bytes == long.MinValue)
+            {
+                return "-" + SizeSuffix(long.MaxValue);
+            }
+
+            if (bytes < 0)
+            {
+                return "-" + SizeSuffix(Math.Abs(bytes));
+            }
+
             var mag = (int)Math.Log(bytes, bytesInKb);
             var adjustedSize = bytes / (decimal)Math.Pow(bytesInKb, mag);
 

src/NzbDrone.Core.Test/FluentTest.cs

@@ -175,7 +175,9 @@ public void MinOrDefault_should_return_zero_when_collection_is_null()
         [TestCase(199, 100, 100)]
         [TestCase(1000, 100, 1000)]
         [TestCase(0, 100, 0)]
-        public void round_to_level(long number, int level, int result)
+        [TestCase(long.MinValue, 1000, -9223372036854775000L)]
+        [TestCase(long.MaxValue, 1000, 9223372036854775000L)]
+        public void round_to_level(long number, int level, long result)
         {
             number.Round(level).Should().Be(result);
         }

src/NzbDrone.Core/Fluent.cs

@@ -22,7 +22,9 @@ public static string WithDefault(this string actual, object defaultValue)
 
         public static long Round(this long number, long level)
         {
-            return Convert.ToInt64(Math.Floor((decimal)number / level) * level);
+            return number < 0
+                ? Convert.ToInt64(Math.Ceiling((decimal)number / level) * level)
+                : Convert.ToInt64(Math.Floor((decimal)number / level) * level);
         }
 
         public static string ToBestDateString(this DateTime dateTime)