Add Fallout effects toggle to graphics settings ☢️ (#4313)

## Summary

Adds a **"Fallout effects"** toggle to the *Effects* section of the
graphics settings modal, letting players disable the nuclear fallout
visuals (useful for performance).

Fallout is rendered by two passes — the broiling green **bloom** on
irradiated territory and its additive **light** contribution in
day/night mode. The bloom pass was already gated by
`passEnabled.falloutBloom`, but the light pass had no gate. This adds a
`passEnabled.falloutLight` flag and a single user-facing
`passEnabled.fallout` graphics override that drives both together.

## Changes

- **`RenderSettings.ts` / `render-settings.json`** — new
`passEnabled.falloutLight` flag (default `true`).
- **`LightmapPass.ts`** — gate the fallout light pass behind
`passEnabled.falloutLight`.
- **`GraphicsOverrides.ts`** — add `fallout: z.boolean()` to the
`passEnabled` override group.
- **`RenderOverrides.ts`** — apply `passEnabled.fallout` to both
`falloutBloom` and `falloutLight`.
- **`GraphicsSettingsModal.ts`** — `currentFallout()` /
`onToggleFallout()` + a toggle button (mirrors the existing Special
Effects toggle).
- **`en.json`** — `graphics_setting.fallout_label` / `fallout_desc`.

## Testing

- `tsc --noEmit` passes; JSON files validated.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/client/hud/layers/GraphicsSettingsModal.ts

@@ -487,6 +487,17 @@ export class GraphicsSettingsModal extends LitElement implements Controller {
     this.patchPassEnabled({ fx: !this.currentSpecialEffects() });
   }
 
+  private currentFallout(): boolean {
+    return (
+      this.userSettings.graphicsOverrides().passEnabled?.fallout ??
+      renderDefaults.passEnabled.falloutBloom
+    );
+  }
+
+  private onToggleFallout() {
+    this.patchPassEnabled({ fallout: !this.currentFallout() });
+  }
+
   /** Whether colorblind mode is currently enabled. */
   private currentColorblind(): boolean {
     return (
@@ -1137,6 +1148,25 @@ export class GraphicsSettingsModal extends LitElement implements Controller {
               </div>
             </button>
 
+            <button
+              class="flex gap-3 items-center w-full text-left p-3 hover:bg-slate-700 rounded-sm text-white transition-colors"
+              @click=${this.onToggleFallout}
+            >
+              <div class="flex-1">
+                <div class="font-medium">
+                  ${translateText("graphics_setting.fallout_label")}
+                </div>
+                <div class="text-sm text-slate-400">
+                  ${translateText("graphics_setting.fallout_desc")}
+                </div>
+              </div>
+              <div class="text-sm text-slate-400">
+                ${this.currentFallout()
+                  ? translateText("user_setting.on")
+                  : translateText("user_setting.off")}
+              </div>
+            </button>
+
             <div
               class="px-3 py-1 text-xs font-semibold text-slate-400 uppercase tracking-wider mt-2"
             >