style(frontend) : apply UI corrections from design review

- Page titles in blue primary (#222783)
- Double main content margins (px-16 py-24)
- Remove blue border above sidebar timer
- Remove project color dot, use project color on title text
- All delete buttons/icons orange (#E2953C)
- Fix collapsed sidebar logo (object-cover object-left)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/pages/admin.vue

@@ -1,6 +1,6 @@
 <template>
     <div>
-        <h1 class="text-2xl font-bold text-neutral-900">Administration</h1>
+        <h1 class="text-2xl font-bold text-primary-500">Administration</h1>
 
         <div class="mt-6 border-b border-neutral-200">
             <nav class="flex gap-6">