refactor: remove unused collections and documentation files

- Deleted the 'index' and 'mcp' collections from content.config.ts.
- Removed the 'docs.md' file containing ArtMCP documentation.
- Deleted the 'index.md' file which served as a welcome page for ArtAPI.

app/pages/docs.vue

@@ -1,8 +1,4 @@
 <script setup lang="ts">
-const { data: _docs } = await useAsyncData('docs', () =>
-  queryCollection('docs').first()
-)
-
 const tools = [
   {
     name: 'activity',
@@ -86,7 +82,7 @@ const apiEndpoints = [
       <UContainer class="py-16">
         <div class="text-center text-white">
           <UBadge
-            color="white"
+            color="neutral"
             variant="subtle"
             size="lg"
             class="mb-4"
@@ -103,7 +99,7 @@ const apiEndpoints = [
             <UButton
               to="/"
               size="lg"
-              color="white"
+              color="neutral"
               variant="solid"
               icon="i-heroicons-arrow-left"
             >
@@ -113,7 +109,7 @@ const apiEndpoints = [
               to="https://github.com/ArthurDanjou/artapi"
               target="_blank"
               size="lg"
-              color="white"
+              color="neutral"
               variant="outline"
               icon="i-simple-icons-github"
             >
@@ -293,7 +289,7 @@ const apiEndpoints = [
                     class="flex gap-2"
                   >
                     <UBadge
-                      color="blue"
+                      color="primary"
                       variant="subtle"
                     >
                       {{ input.name }}
@@ -398,7 +394,7 @@ const apiEndpoints = [
             class="flex items-center gap-3 p-3 rounded-lg hover:bg-gray-100 dark:hover:bg-gray-800 transition-colors"
           >
             <UBadge
-              color="green"
+              color="success"
               variant="subtle"
               class="font-mono text-xs"
             >