Add persistent global mouse sensitivity setting with slider

MouseSensitivity is a static, PlayerPrefs-backed multiplier (default 1,
clamped 0.1-4.0) that scales the mouse-look delta in the FreeCam,
FirstPerson and ThirdPerson controllers. Writes flush immediately so the
value survives a hard build exit. MouseSensitivitySlider binds the
Settings-panel slider to it (range read from the inspector) and mirrors
the value into its label, syncing on panel open via OnEnable.

Main.unity now contains the session-manager canvas directly (the
Online Session Manager prefab was unpacked) and wires the slider binder.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/MouseSensitivitySlider.cs

@@ -0,0 +1,37 @@
+using TMPro;
+using UnityEngine;
+using UnityEngine.UI;
+
+/// Binds a UI Slider (and optional value label) to the global MouseSensitivity
+/// multiplier. The slider's range is authored in the inspector (0.1 - 4.0);
+/// this only reads/writes the value so scene-side range edits are respected.
+public class MouseSensitivitySlider : MonoBehaviour
+{
+    [SerializeField] private Slider slider;
+    [Tooltip("Optional TMP label showing the current multiplier (e.g. \"1,00\").")]
+    [SerializeField] private TMP_Text valueLabel;
+
+    void OnEnable()
+    {
+        if (!slider) return;
+        slider.SetValueWithoutNotify(MouseSensitivity.Multiplier);
+        UpdateLabel(MouseSensitivity.Multiplier);
+        slider.onValueChanged.AddListener(OnSliderChanged);
+    }
+
+    void OnDisable()
+    {
+        if (slider) slider.onValueChanged.RemoveListener(OnSliderChanged);
+    }
+
+    void OnSliderChanged(float value)
+    {
+        MouseSensitivity.Multiplier = value;
+        UpdateLabel(value);
+    }
+
+    void UpdateLabel(float value)
+    {
+        if (valueLabel) valueLabel.text = value.ToString("0.00");
+    }
+}