Add Graphics Settings name color toggle and unit tests

Adds a single "Name color" toggle (Colored / Black) to the Graphics
Settings modal, backed by a `darkNames` boolean in the override schema
that derives the five underlying name-rendering fields
(fill/outline player-color flags + static outline RGB). Forcing the
outline RGB to 0 in dark mode is what makes the shader's defaultFill
ramp actually render black — flipping the boolean uniforms alone
wasn't enough because the fill is derived from uOutlineColor when
fillUsePlayerColor is false.

Flips the render-settings.json defaults so black names are the
renderer baseline; the modal's no-override state follows the JSON
source of truth. Adds tests covering schema parse behavior and the
generateRenderSettings derivation for each override field.

src/client/render/gl/render-settings.json

@@ -160,11 +160,11 @@
     "nameScaleCap": 3,
     "troopSizeMultiplier": 0.6,
     "outlineWidth": 1.4,
-    "outlineR": 1.0,
-    "outlineG": 1.0,
-    "outlineB": 1.0,
-    "outlineUsePlayerColor": false,
-    "fillUsePlayerColor": true,
+    "outlineR": 0.0,
+    "outlineG": 0.0,
+    "outlineB": 0.0,
+    "outlineUsePlayerColor": true,
+    "fillUsePlayerColor": false,
     "emojiRowOffset": 1.4,
     "statusRowOffset": 1.4
   },