feat: add glassmorphism design system

Dark-first color palette, glass surface styles with blur
backing, typography with text shadows, and spacing constants.

src/theme/glass.ts

@@ -0,0 +1,55 @@
+import { Platform, ViewStyle } from "react-native";
+import { colors } from "./colors";
+
+export const glassIntensity = {
+  subtle: 15,
+  medium: 25,
+  strong: 40,
+  heavy: 60,
+} as const;
+
+export type GlassVariant = "subtle" | "medium" | "strong" | "heavy";
+
+export const glassSurface = (
+  variant: GlassVariant = "medium"
+): ViewStyle => ({
+  backgroundColor: colors.glass.background,
+  borderWidth: 1,
+  borderColor: colors.glass.border,
+  overflow: "hidden",
+  ...Platform.select({
+    ios: {
+      shadowColor: colors.shadow.soft,
+      shadowOffset: { width: 0, height: 8 },
+      shadowOpacity: variant === "strong" ? 0.3 : 0.15,
+      shadowRadius: 24,
+    },
+    android: {
+      elevation: variant === "strong" ? 12 : 6,
+    },
+  }),
+});
+
+export const glassRadius = {
+  xs: 8,
+  sm: 12,
+  md: 16,
+  lg: 24,
+  xl: 32,
+  pill: 999,
+} as const;
+
+export const glassBorder = {
+  thin: {
+    borderWidth: 0.5,
+    borderColor: colors.glass.border,
+  },
+  normal: {
+    borderWidth: 1,
+    borderColor: colors.glass.border,
+  },
+  accent: {
+    borderWidth: 1,
+    borderColor: colors.glass.borderLight,
+  },
+} as const;