feat(sprint-3): apply Survey Teal field UI

FieldLogger/Resources/Styles/ThemeManager.cs

@@ -0,0 +1,38 @@
+namespace FieldLogger.Resources.Styles;
+
+public enum UlThemeMode
+{
+    Default,
+    Sunlight,
+}
+
+/// <summary>Applies generated semantic colors. Call on the UI thread after app resources initialize.</summary>
+public static class ThemeManager
+{
+    private static readonly string[] SemanticColors =
+    [
+        "Canvas", "Surface", "SurfaceRaised", "SurfaceStrong", "Text", "TextMuted",
+        "Primary", "PrimaryPressed", "Accent", "Border", "Focus", "Map", "Success",
+        "Warning", "Error", "Neutral", "Disabled", "OnStrong", "OnPrimary", "OnAccent",
+    ];
+
+    public static UlThemeMode Current { get; private set; } = UlThemeMode.Default;
+
+    public static void Apply(UlThemeMode mode)
+    {
+        var resources = Application.Current?.Resources
+            ?? throw new InvalidOperationException("Application resources are not initialized.");
+        var prefix = mode == UlThemeMode.Sunlight ? "UlSunlightColor" : "UlDefaultColor";
+
+        foreach (var name in SemanticColors)
+        {
+            if (!resources.TryGetValue($"{prefix}{name}", out var value) || value is not Color color)
+            {
+                throw new InvalidOperationException($"Generated theme token {prefix}{name} is missing.");
+            }
+            resources[$"UlColor{name}"] = color;
+            resources[$"UlBrush{name}"] = new SolidColorBrush(color);
+        }
+        Current = mode;
+    }
+}