feat(web): add theme definition system with 5 built-in themes (#493)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/themes/nord.ts

@@ -0,0 +1,45 @@
+import type { ThemeDefinition } from "./types";
+
+/**
+ * Nord theme — Arctic, north-bluish palette.
+ * Based on https://www.nordtheme.com/
+ */
+export const nordTheme: ThemeDefinition = {
+  id: "nord",
+  name: "Nord",
+  description: "Arctic, north-bluish color palette inspired by the beauty of the arctic",
+  author: "Arctic Ice Studio",
+  isDark: true,
+  colorPreview: ["#2e3440", "#3b4252", "#eceff4", "#5e81ac", "#b48ead"],
+  colors: {
+    "bg-950": "#242933",
+    "bg-900": "#2e3440",
+    "bg-850": "#333a47",
+    "surface-800": "#3b4252",
+    "surface-750": "#434c5e",
+    "border-700": "#4c566a",
+    "text-100": "#eceff4",
+    "text-300": "#d8dee9",
+    "text-500": "#7b88a1",
+    "blue-500": "#5e81ac",
+    "blue-400": "#81a1c1",
+    "red-500": "#bf616a",
+    "red-400": "#d08787",
+    "purple-500": "#b48ead",
+    "purple-400": "#c4a5bf",
+    "teal-500": "#8fbcbb",
+    "teal-400": "#88c0d0",
+    "amber-500": "#ebcb8b",
+    "amber-400": "#f0d8a8",
+    "pink-500": "#c97fba",
+    "emerald-500": "#a3be8c",
+    "orange-500": "#d08770",
+    "cyan-500": "#88c0d0",
+    "indigo-500": "#7b88a1",
+  },
+  shadows: {
+    sm: "0 1px 2px 0 rgb(0 0 0 / 0.25)",
+    md: "0 4px 6px -1px rgb(0 0 0 / 0.35), 0 2px 4px -2px rgb(0 0 0 / 0.25)",
+    lg: "0 10px 15px -3px rgb(0 0 0 / 0.4), 0 4px 6px -4px rgb(0 0 0 / 0.35)",
+  },
+};