style: refine design system aesthetics to flat solid dark-mode theme

templates/auth/register.html

@@ -6,7 +6,7 @@
 {% block content %}
 <div class="grow flex items-center justify-center py-12 px-4 sm:px-6 lg:px-8">
     <div class="max-w-md w-full bg-[#1e293b]/40 backdrop-blur-xl border border-slate-900 rounded-3xl p-8 shadow-2xl relative overflow-hidden">
-        <div class="absolute top-0 left-0 w-full h-1 bg-gradient-to-r from-emerald-400 via-teal-500 to-cyan-600"></div>
+        <div class="absolute top-0 left-0 w-full h-1 bg-emerald-500"></div>
         
         <div class="text-center mb-8">
             <h2 class="text-3xl font-extrabold text-slate-100 tracking-tight">Create Account</h2>
@@ -37,7 +37,7 @@
             {{ ui::text_input(id="password", name="password", label="Password", type="password", placeholder="••••••••", required=true) }}
 
             <div>
-                {{ ui::button(label="Sign Up", variant="primary", type="submit", extra_class="w-full py-3.5 bg-gradient-to-r from-emerald-500 to-teal-600 hover:opacity-95 text-white shadow-lg shadow-emerald-500/10 focus:ring-emerald-500") }}
+                {{ ui::button(label="Sign Up", variant="primary", type="submit", extra_class="w-full py-3.5 bg-emerald-600 hover:bg-emerald-700 text-white shadow-lg shadow-emerald-500/10 focus:ring-emerald-500") }}
             </div>
         </form>