refactor: remove SearXNG references and rename binary to kafka

- Rename cmd/searxng-go to cmd/kafka
- Remove all SearXNG references from source comments while keeping
  "SearXNG-compatible API" in user-facing docs
- Update binary paths in README, CLAUDE.md, and Dockerfile
- Update log message to "kafka starting"

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

internal/engines/qwant.go

@@ -14,11 +14,11 @@ import (
 	"github.com/PuerkitoBio/goquery"
 )
 
-// QwantEngine implements a SearXNG-like `qwant` (web) adapter using
+// QwantEngine implements a `qwant` (web) adapter using
 // Qwant v3 endpoint: https://api.qwant.com/v3/search/web.
 //
-// Qwant's API is not fully documented; this mirrors SearXNG's parsing logic
-// for the `web` category from `.agent/searxng/searx/engines/qwant.py`.
+// Qwant's API is not fully documented; this implements parsing logic
+// for the `web` category.
 type QwantEngine struct {
 	client        *http.Client
 	category      string // "web" (JSON API) or "web-lite" (HTML fallback)
@@ -37,7 +37,7 @@ func (e *QwantEngine) Search(ctx context.Context, req contracts.SearchRequest) (
 		return contracts.SearchResponse{Query: req.Query}, nil
 	}
 
-	// For API parity we use SearXNG web defaults: count=10, offset=(pageno-1)*count.
+	// For API parity we use web defaults: count=10, offset=(pageno-1)*count.
 	// The engine's config field exists so we can expand to news/images/videos later.
 	count := e.resultsPerPage
 	if count <= 0 {
@@ -262,7 +262,7 @@ func (e *QwantEngine) searchWebLite(ctx context.Context, req contracts.SearchReq
 			return
 		}
 
-		// In SearXNG: "./span[contains(@class, 'url partner')]"
+		// Selector: "./span[contains(@class, 'url partner')]"
 		urlText := strings.TrimSpace(item.Find("span.url.partner").First().Text())
 		if urlText == "" {
 			// fallback: any span with class containing both 'url' and 'partner'