refactor(frontend): port search-zen-50 style to Go templates

Replace React SPA with simple Go templates using search-zen-50
visual style. No JavaScript required - pure HTML/CSS with clean
teal accent color scheme, monospace logo, and minimal design.

- Simplified base.html without HTMX or autocomplete JS
- Clean homepage with centered search box
- Results page with sticky header and category tabs
- Simplified CSS matching search-zen-50 aesthetics

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

internal/views/templates/results.html

@@ -1,58 +1,38 @@
 {{define "title"}}{{if .Query}}{{.Query}} — {{end}}{{end}}
 {{define "content"}}
-<div class="results-layout">
-  <!-- Compact search bar spans all columns -->
-  <div class="search-compact">
-    <div class="search-box">
-      <form method="GET" action="/search" role="search" id="search-form">
-        <input type="text" name="q" id="q" value="{{.Query}}" autocomplete="off" autofocus
-          hx-get="/search" hx-target="#results" hx-trigger="keyup changed delay:500ms" hx-include="this">
-        <button type="submit" class="search-box-submit" aria-label="Search">
-          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
+<div class="results-container">
+  <div class="results-header">
+    <a href="/" class="results-logo">
+      <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
+        <circle cx="11" cy="11" r="8"/>
+        <path d="m21 21-4.35-4.35"/>
+      </svg>
+      <span>kafka</span>
+    </a>
+
+    <form class="header-search" method="GET" action="/search" role="search">
+      <div class="search-box">
+        <input type="text" name="q" value="{{.Query}}" placeholder="Search…" autocomplete="off">
+        <button type="submit" class="search-btn" aria-label="Search">
+          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
             <circle cx="11" cy="11" r="8"/>
             <path d="m21 21-4.35-4.35"/>
           </svg>
         </button>
-      </form>
-    </div>
+      </div>
+    </form>
   </div>
 
-  <!-- Center: Results -->
-  <div class="results-column" id="results">
+  <div class="category-tabs" role="tablist">
+    <a href="/search?q={{.Query | urlquery}}&category=" class="category-tab {{if eq .ActiveCategory ""}}active{{end}}">All</a>
+    <a href="/search?q={{.Query | urlquery}}&category=general" class="category-tab {{if eq .ActiveCategory "general"}}active{{end}}">General</a>
+    <a href="/search?q={{.Query | urlquery}}&category=it" class="category-tab {{if eq .ActiveCategory "it"}}active{{end}}">IT</a>
+    <a href="/search?q={{.Query | urlquery}}&category=news" class="category-tab {{if eq .ActiveCategory "news"}}active{{end}}">News</a>
+    <a href="/search?q={{.Query | urlquery}}&category=images" class="category-tab {{if eq .ActiveCategory "images"}}active{{end}}">Images</a>
+  </div>
+
+  <div class="results-content">
     {{template "results_inner" .}}
   </div>
-
-  <!-- Right: Knowledge Panel + Related Searches -->
-  <aside class="right-column" id="right-column">
-    {{if and .Infoboxes (gt (len .Infoboxes) 0)}}
-    {{with index .Infoboxes 0}}
-    <div class="knowledge-panel">
-      {{if .img_src}}<img class="knowledge-panel-thumb" src="{{.img_src}}" alt="{{.title}}" loading="lazy">{{end}}
-      {{if .title}}<div class="knowledge-panel-title">{{.title}}</div>{{end}}
-      {{if .content}}<div class="knowledge-panel-content">{{.content}}</div>{{end}}
-    </div>
-    {{end}}
-    {{end}}
-
-    {{if .Suggestions}}
-    <div class="sidebar-card">
-      <div class="sidebar-card-title">Related Searches</div>
-      <div class="related-searches">
-        {{range .Suggestions}}
-        <a class="related-search-link" href="/search?q={{. | urlquery}}">{{.}}</a>
-        {{end}}
-      </div>
-    </div>
-    {{end}}
-
-    {{if .UnresponsiveEngines}}
-    <div class="sidebar-card">
-      <div class="sidebar-card-title">Engine Status</div>
-      <ul class="unresponsive-engines">
-        {{range .UnresponsiveEngines}}<li>{{index . 0}}: {{index . 1}}</li>{{end}}
-      </ul>
-    </div>
-    {{end}}
-  </aside>
 </div>
 {{end}}