feat(effects): extinguish fire with water/rain and ambient SFX volume

Water and rain erase fire under a tight brush hit radius; add looping fire/rain ambients and an Effects sound slider that also scales one-shot effect SFX.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/control/effectsSfxGain.ts

@@ -0,0 +1,17 @@
+/** Общая громкость звуков эффектов (огонь ambient + one-shot). 0…1. */
+
+let effectsSfxGain = 0.75;
+
+export function clampEffectsSfxGain(v: number): number {
+  if (!Number.isFinite(v)) return 0.75;
+  return Math.max(0, Math.min(1, v));
+}
+
+export function getEffectsSfxGain(): number {
+  return effectsSfxGain;
+}
+
+export function setEffectsSfxGain(v: number): number {
+  effectsSfxGain = clampEffectsSfxGain(v);
+  return effectsSfxGain;
+}