feat(ui): dark theme redesign, fix image search and defaults

- Inline CSS in base.html (Inter, dark mode, sticky search, tabs, results)
- Remove HTMX/JS from templates; pagination via GET links
- Atmospheric side gradients + grid; wider column on large viewports
- Parse ?category= for HTML tabs (fixes Images category routing)
- Include bing_images, ddg_images, qwant_images in local_ported defaults
- Default listen port 5355; update Docker, compose, flake, README
- Favicon img uses /favicon/ proxy; preferences without inline JS

Made-with: Cursor

internal/views/templates/video_item.html

@@ -1,5 +1,5 @@
 {{define "video_item"}}
-<article class="result video-result">
+<article class="result video-result" data-engine="{{.Engine}}">
   {{if .Thumbnail}}
   <div class="result_thumbnail">
     <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">
@@ -9,13 +9,16 @@
   {{end}}
   <div class="result_content_wrapper">
     <div class="result_header">
-      <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.Title}}</a>
+      <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.SafeTitle}}</a>
     </div>
     <div class="result_url">
-      <span class="engine-badge">youtube</span>
+      {{if .URL}}
+      <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.URL}}</a>
+      {{end}}
+      <span class="engine-badge" data-engine="{{.Engine}}">{{.Engine}}</span>
     </div>
     {{if .Content}}
-    <p class="result_content">{{.Content}}</p>
+    <p class="result_content">{{.SafeContent}}</p>
     {{end}}
   </div>
 </article>