feat: complete UI redesign — modern, clean search interface

- New CSS: complete design system with CSS variables, modern color palette
- Homepage: full-viewport hero with centered search, logo, tagline
- Result cards: rounded, shadowed, with favicons via Google Favicon API
- Layout: sidebar + results grid, responsive
- Typography: proper font stack, variable weights
- Settings panel: polished popover with animations
- Autocomplete: modern dropdown with keyboard nav
- Dark mode: full color palette via data-theme attribute
- Favicon: clean search icon SVG

internal/views/templates/result_item.html

@@ -1,16 +1,15 @@
 {{define "result_item"}}
 <article class="result">
-  <h3 class="result_header">
+  <div class="result_header">
     <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.Title}}</a>
-  </h3>
+  </div>
   <div class="result_url">
+    <img class="result-favicon" src="https://www.google.com/s2/favicons?domain={{.URL | urlquery}}&sz=32" alt="" loading="lazy" onerror="this.style.display='none'">
     <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.URL}}</a>
+    <span class="engine-badge">{{.Engine}}</span>
   </div>
   {{if .Content}}
   <p class="result_content">{{.Content}}</p>
   {{end}}
-  {{if .Engine}}
-  <div class="result_engine"><span class="engine">{{.Engine}}</span></div>
-  {{end}}
 </article>
 {{end}}