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

cmd/searxng-go/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"io/fs"
 	"log"
 	"log/slog"
 	"net/http"
@@ -13,6 +14,7 @@ import (
 	"github.com/ashie/gosearch/internal/httpapi"
 	"github.com/ashie/gosearch/internal/middleware"
 	"github.com/ashie/gosearch/internal/search"
+	"github.com/ashie/gosearch/internal/views"
 )
 
 func main() {
@@ -38,8 +40,7 @@ func main() {
 	defer searchCache.Close()
 
 	// Seed env vars from config so existing engine/factory/planner code
-	// picks them up without changes. The config layer is the single source
-	// of truth; env vars remain as overrides via applyEnvOverrides.
+	// picks them up without changes.
 	if len(cfg.Engines.LocalPorted) > 0 {
 		os.Setenv("LOCAL_PORTED_ENGINES", cfg.LocalPortedCSV())
 	}
@@ -59,9 +60,18 @@ func main() {
 	h := httpapi.NewHandler(svc)
 
 	mux := http.NewServeMux()
+	mux.HandleFunc("/", h.Index)
 	mux.HandleFunc("/healthz", h.Healthz)
 	mux.HandleFunc("/search", h.Search)
 
+	// Serve embedded static files (CSS, JS, images).
+	staticFS, err := views.StaticFS()
+	if err != nil {
+		log.Fatalf("failed to load static files: %v", err)
+	}
+	var subFS fs.FS = staticFS
+	mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(subFS))))
+
 	// Apply middleware: rate limiter → CORS → handler.
 	var handler http.Handler = mux
 	handler = middleware.CORS(middleware.CORSConfig{