refactor(settings): simplify GC aggressiveness to Off/Light only

Remove Moderate, Heavy, and Extreme GC aggressiveness levels, keeping only Off and Light options for simpler configuration.

- Light mode now uses 75%/90% VRAM thresholds

- Simplified switch statements in texture/buffer cache

- Updated UI dropdowns for desktop and Android

- Light is now the default and recommended setting

src/common/settings.h

@@ -520,9 +520,9 @@ struct Values {
 
     // GC aggressiveness level for texture/buffer cache eviction
     SwitchableSetting<GCAggressiveness, true> gc_aggressiveness{linkage,
-                                                                 GCAggressiveness::Moderate,
+                                                                 GCAggressiveness::Light,
                                                                  GCAggressiveness::Off,
-                                                                 GCAggressiveness::Extreme,
+                                                                 GCAggressiveness::Light,
                                                                  "gc_aggressiveness",
                                                                  Category::RendererAdvanced,
                                                                  Specialization::Default,