🔦 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/PlayerFlashlightState.cs

@@ -0,0 +1,18 @@
+using CounterStrikeSharp.API.Core;
+
+namespace Flashlight;
+
+public sealed class PlayerFlashlightState
+{
+    public bool IsOn { get; set; }
+    public bool CanToggle { get; set; } = true;
+    public bool WasUsePressed { get; set; }
+    public CBarnLight? Light { get; set; }
+
+    public void Reset()
+    {
+        IsOn = false;
+        CanToggle = true;
+        WasUsePressed = false;
+    }
+}