fix: disable SSR + add app.config for Nuxt UI colors

SSR causes 'Cannot read properties of null' with Nuxt UI v3 color
mode. Since this is an internal app, SPA mode works fine.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/app.config.ts

@@ -0,0 +1,8 @@
+export default defineAppConfig({
+  ui: {
+    colors: {
+      primary: 'indigo',
+      neutral: 'zinc',
+    },
+  },
+})

nuxt.config.ts

@@ -1,6 +1,7 @@
 export default defineNuxtConfig({
   compatibilityDate: '2025-01-01',
   future: { compatibilityVersion: 4 },
+  ssr: false,
   modules: ['@nuxt/ui'],
 
   runtimeConfig: {