feat: HTMX + Go Templates HTML frontend

- Add internal/views/ package with embedded templates and static files
- Go html/template with SearXNG-compatible CSS class names
- Dark mode via prefers-color-scheme, responsive layout, print styles
- HTMX integration:
  - Debounced instant search (500ms) on the search input
  - Form submission targets #results via hx-post
  - Pagination buttons are HTMX-powered (swap results div only)
  - HX-Request header detection for fragment vs full page rendering
- Template structure:
  - base.html: full page layout with HTMX script, favicon, CSS
  - index.html: homepage with centered search box
  - results.html: full results page (wraps base + results_inner)
  - results_inner.html: results fragment (HTMX partial + sidebar + pagination)
  - result_item.html: reusable result article partial
- Smart format detection: browser requests (Accept: text/html) default to HTML,
  API clients default to JSON
- Static files served at /static/ from embedded FS (CSS, favicon SVG)
- Index route at GET /
- Empty query on HTML format redirects to homepage
- Custom CSS (gosearch.css): clean, minimal, privacy-respecting aesthetic
  with light/dark mode, responsive breakpoints, print stylesheet
- Add views package tests

internal/views/templates/results_inner.html

@@ -0,0 +1,107 @@
+{{define "results_inner"}}
+{{if .Corrections}}
+<div class="corrections">
+  {{range .Corrections}}<span class="correction">{{.}}</span>{{end}}
+</div>
+{{end}}
+
+{{if .Answers}}
+<div id="answers">
+  {{range .Answers}}
+  <div class="answer">{{.}}</div>
+  {{end}}
+</div>
+{{end}}
+
+<div id="sidebar">
+  {{if .NumberOfResults}}
+  <p id="result_count"><small>{{.NumberOfResults}} results</small></p>
+  {{end}}
+
+  {{if .Infoboxes}}
+  <div id="infoboxes">
+    {{range .Infoboxes}}
+    <div class="infobox">
+      {{if .title}}<div class="title">{{.title}}</div>{{end}}
+      {{if .content}}<div class="content">{{.content}}</div>{{end}}
+      {{if .img_src}}<img src="{{.img_src}}" alt="{{.title}}" loading="lazy">{{end}}
+    </div>
+    {{end}}
+  </div>
+  {{end}}
+
+  {{if .Suggestions}}
+  <div id="suggestions">
+    <small>Suggestions:</small>
+    <div>
+      {{range .Suggestions}}<span class="suggestion"><a href="/search?q={{.}}">{{.}}</a></span>{{end}}
+    </div>
+  </div>
+  {{end}}
+
+  {{if .UnresponsiveEngines}}
+  <div class="unresponsive_engines">
+    <small>Unresponsive engines:</small>
+    <ul>
+      {{range .UnresponsiveEngines}}<li>{{index . 0}}: {{index . 1}}</li>{{end}}
+    </ul>
+  </div>
+  {{end}}
+</div>
+
+<div id="urls" role="main">
+  {{if .Results}}
+  {{range .Results}}
+  {{template "result_item" .}}
+  {{end}}
+  {{else if not .Answers}}
+  <div class="no_results">
+    <p>No results found.</p>
+    {{if .Query}}<p>Try different keywords or check your spelling.</p>{{end}}
+  </div>
+  {{end}}
+</div>
+
+{{if .Pageno}}
+<nav id="pagination" role="navigation">
+  {{if gt .Pageno 1}}
+  <form method="GET" action="/search" class="previous_page">
+    <input type="hidden" name="q" value="{{.Query}}">
+    <input type="hidden" name="pageno" value="{{.PrevPage}}">
+    <input type="hidden" name="format" value="html">
+    <button type="submit" role="link">← Previous</button>
+  </form>
+  {{end}}
+
+  <div class="numbered_pagination">
+    {{range .PageNumbers}}
+    {{if .IsCurrent}}
+    <span class="page_number_current">{{.Num}}</span>
+    {{else}}
+    <form method="GET" action="/search" class="page_number">
+      <input type="hidden" name="q" value="{{$.Query}}">
+      <input type="hidden" name="pageno" value="{{.Num}}">
+      <input type="hidden" name="format" value="html">
+      <button type="submit" role="link">{{.Num}}</button>
+    </form>
+    {{end}}
+    {{end}}
+  </div>
+
+  {{if .HasNext}}
+  <form method="GET" action="/search" class="next_page">
+    <input type="hidden" name="q" value="{{.Query}}">
+    <input type="hidden" name="pageno" value="{{.NextPage}}">
+    <input type="hidden" name="format" value="html">
+    <button type="submit" role="link">Next →</button>
+  </form>
+  {{end}}
+</nav>
+{{end}}
+
+<div id="backToTop">
+  <a href="#">↑ Back to top</a>
+</div>
+
+<div class="htmx-indicator">Searching…</div>
+{{end}}