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/engines/wikipedia_test.go

@@ -0,0 +1,61 @@
+package engines
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/ashie/gosearch/internal/contracts"
+)
+
+func TestWikipediaEngine_Search(t *testing.T) {
+	transport := roundTripperFunc(func(r *http.Request) (*http.Response, error) {
+		if r.Method != http.MethodGet {
+			return httpResponse(http.StatusMethodNotAllowed, "", ""), nil
+		}
+		if r.URL.Host != "en.wikipedia.org" {
+			return httpResponse(http.StatusNotFound, "", ""), nil
+		}
+
+		if r.URL.Path != "/api/rest_v1/page/summary/Taxi" {
+			return httpResponse(http.StatusNotFound, "", ""), nil
+		}
+
+		body := `{
+  "title": "Taxi",
+  "description": "A car",
+  "titles": { "display": "Taxi" },
+  "content_urls": { "desktop": { "page": "https://en.wikipedia.org/wiki/Taxi" } }
+}`
+		return httpResponse(http.StatusOK, body, "application/json"), nil
+	})
+
+	client := &http.Client{Transport: transport}
+	engine := &WikipediaEngine{client: client}
+
+	resp, err := engine.Search(context.Background(), contracts.SearchRequest{
+		Query:  "Taxi",
+		Pageno: 1,
+		Language: "en",
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(resp.Results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(resp.Results))
+	}
+	r := resp.Results[0]
+	if r.Title != "Taxi" {
+		t.Fatalf("expected title Taxi, got %q", r.Title)
+	}
+	if r.Content != "A car" {
+		t.Fatalf("expected content, got %q", r.Content)
+	}
+	if r.URL == nil || *r.URL == "" {
+		t.Fatalf("expected url, got nil/empty")
+	}
+	if *r.URL != "https://en.wikipedia.org/wiki/Taxi" {
+		t.Fatalf("unexpected url: %q", *r.URL)
+	}
+}
+