🔦 Modernize flashlight for CSS/.NET 10

Bump to CounterStrikeSharp 1.0.371 and .NET 10, replace per-tick light
spawns with a parented light_barn, add plugin config, real unit tests,
and refresh CI plus docs.

Co-authored-by: Cursor <cursoragent@cursor.com>

Flashlight/FlashlightLogic.cs

@@ -0,0 +1,62 @@
+using System.Numerics;
+
+namespace Flashlight;
+
+public static class FlashlightLogic
+{
+    public static bool TryToggle(ref bool isOn, ref bool canToggle)
+    {
+        if (!canToggle)
+        {
+            return false;
+        }
+
+        isOn = !isOn;
+        canToggle = false;
+        return true;
+    }
+
+    public static bool IsUsePressedEdge(bool usePressed, bool wasUsePressed)
+    {
+        return usePressed && !wasUsePressed;
+    }
+
+    public static float GetEyeOffsetZ(bool isCrouching, float standOffset, float crouchOffset)
+    {
+        return isCrouching ? crouchOffset : standOffset;
+    }
+
+    public static Vector3 CalculateLightOrigin(
+        Vector3 pawnOrigin,
+        Vector3 forward,
+        float eyeOffsetZ,
+        float forwardDistance)
+    {
+        return new Vector3(
+            pawnOrigin.X + forward.X * forwardDistance,
+            pawnOrigin.Y + forward.Y * forwardDistance,
+            pawnOrigin.Z + eyeOffsetZ + forward.Z * forwardDistance);
+    }
+
+    public static Vector3 ForwardFromAnglesDegrees(float pitch, float yaw)
+    {
+        var pitchRad = pitch * (MathF.PI / 180f);
+        var yawRad = yaw * (MathF.PI / 180f);
+        var cosPitch = MathF.Cos(pitchRad);
+
+        return new Vector3(
+            cosPitch * MathF.Cos(yawRad),
+            cosPitch * MathF.Sin(yawRad),
+            -MathF.Sin(pitchRad));
+    }
+
+    public static bool ShouldCreateLight(bool isOn, bool hasValidLight)
+    {
+        return isOn && !hasValidLight;
+    }
+
+    public static bool ShouldDestroyLight(bool isOn, bool hasValidLight)
+    {
+        return !isOn && hasValidLight;
+    }
+}