feat: build Go-based SearXNG-compatible search service

Implement an API-first Go rewrite with local engine adapters, upstream fallback, and Nix-based tooling so searches can run without matching the original UI while preserving response compatibility.

Made-with: Cursor

internal/httpapi/handlers.go

@@ -0,0 +1,41 @@
+package httpapi
+
+import (
+	"net/http"
+
+	"github.com/ashie/gosearch/internal/search"
+)
+
+type Handler struct {
+	searchSvc *search.Service
+}
+
+func NewHandler(searchSvc *search.Service) *Handler {
+	return &Handler{searchSvc: searchSvc}
+}
+
+func (h *Handler) Healthz(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte("OK"))
+}
+
+func (h *Handler) Search(w http.ResponseWriter, r *http.Request) {
+	req, err := search.ParseSearchRequest(r)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	resp, err := h.searchSvc.Search(r.Context(), req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if err := search.WriteSearchResponse(w, req.Format, resp); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+}
+