feat: add image search with Bing, DuckDuckGo, and Qwant engines

Three new image search engines:
- bing_images: Bing Images via RSS endpoint
- ddg_images: DuckDuckGo Images via VQD API
- qwant_images: Qwant Images via v3 search API

Frontend:
- Image grid layout with responsive columns
- image_item template with thumbnail, title, and source metadata
- Hover animations and lazy loading
- Grid activates automatically when category=images

Backend:
- category=images routes to image engines via planner
- Image engines registered in factory and engine allowlist
- extractImgSrc helper for parsing thumbnail URLs from HTML
- IsImageSearch flag on PageData for template layout switching

internal/engines/qwant_images.go

@@ -0,0 +1,199 @@
+// kafka — a privacy-respecting metasearch engine
+// Copyright (C) 2026-present metamorphosis-dev
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+package engines
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/metamorphosis-dev/kafka/internal/contracts"
+)
+
+// QwantImagesEngine searches Qwant Images via the v3 search API.
+type QwantImagesEngine struct {
+	client *http.Client
+}
+
+func (e *QwantImagesEngine) Name() string { return "qwant_images" }
+
+func (e *QwantImagesEngine) Search(ctx context.Context, req contracts.SearchRequest) (contracts.SearchResponse, error) {
+	if e == nil || e.client == nil {
+		return contracts.SearchResponse{}, errors.New("qwant_images engine not initialized")
+	}
+	q := strings.TrimSpace(req.Query)
+	if q == "" {
+		return contracts.SearchResponse{Query: req.Query}, nil
+	}
+
+	args := url.Values{}
+	args.Set("q", req.Query)
+	args.Set("count", "20")
+	args.Set("locale", qwantLocale(req.Language))
+	args.Set("safesearch", fmt.Sprintf("%d", req.Safesearch))
+	args.Set("offset", fmt.Sprintf("%d", (req.Pageno-1)*20))
+
+	endpoint := "https://api.qwant.com/v3/search/images?" + args.Encode()
+
+	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+	if err != nil {
+		return contracts.SearchResponse{}, err
+	}
+	httpReq.Header.Set("User-Agent", "kafka/0.1 (compatible; +https://git.ashisgreat.xyz/penal-colony/kafka)")
+
+	resp, err := e.client.Do(httpReq)
+	if err != nil {
+		return contracts.SearchResponse{}, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusForbidden {
+		return contracts.SearchResponse{
+			Query:               req.Query,
+			UnresponsiveEngines: [][2]string{{"qwant_images", "captcha_or_js_block"}},
+			Results:             []contracts.MainResult{},
+			Answers:             []map[string]any{},
+			Corrections:         []string{},
+			Infoboxes:           []map[string]any{},
+			Suggestions:         []string{},
+		}, nil
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		io.Copy(io.Discard, io.LimitReader(resp.Body, 16*1024))
+		return contracts.SearchResponse{}, fmt.Errorf("qwant_images upstream error: status %d", resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
+	if err != nil {
+		return contracts.SearchResponse{}, err
+	}
+
+	return parseQwantImages(body, req.Query)
+}
+
+func parseQwantImages(body []byte, query string) (contracts.SearchResponse, error) {
+	var top map[string]any
+	if err := json.Unmarshal(body, &top); err != nil {
+		return contracts.SearchResponse{}, fmt.Errorf("qwant_images JSON parse error: %w", err)
+	}
+
+	status, _ := top["status"].(string)
+	if status != "success" {
+		return contracts.SearchResponse{
+			Query:               query,
+			UnresponsiveEngines: [][2]string{{"qwant_images", "api_error"}},
+			Results:             []contracts.MainResult{},
+			Answers:             []map[string]any{},
+			Corrections:         []string{},
+			Infoboxes:           []map[string]any{},
+			Suggestions:         []string{},
+		}, nil
+	}
+
+	data, _ := top["data"].(map[string]any)
+	result, _ := data["result"].(map[string]any)
+	items, _ := result["items"].(map[string]any)
+	mainline := items["mainline"]
+
+	rows := toSlice(mainline)
+	if len(rows) == 0 {
+		return contracts.SearchResponse{
+			Query:               query,
+			NumberOfResults:    0,
+			Results:             []contracts.MainResult{},
+			Answers:             []map[string]any{},
+			Corrections:         []string{},
+			Infoboxes:           []map[string]any{},
+			Suggestions:         []string{},
+			UnresponsiveEngines: [][2]string{},
+		}, nil
+	}
+
+	out := make([]contracts.MainResult, 0)
+	for _, row := range rows {
+		rowMap, ok := row.(map[string]any)
+		if !ok {
+			continue
+		}
+		rowType, _ := rowMap["type"].(string)
+		if rowType != "images" {
+			continue
+		}
+
+		rowItems := toSlice(rowMap["items"])
+		for _, it := range rowItems {
+			itemMap, ok := it.(map[string]any)
+			if !ok {
+				continue
+			}
+			title := toString(itemMap["title"])
+			resURL := toString(itemMap["url"])
+			thumb := toString(itemMap["thumbnail"])
+			fullImg := toString(itemMap["media"])
+			source := toString(itemMap["source"])
+
+			if resURL == "" && fullImg == "" {
+				continue
+			}
+
+			// Use the source page URL for the link, full image for thumbnail display.
+			linkPtr := resURL
+			if linkPtr == "" {
+				linkPtr = fullImg
+			}
+			displayThumb := fullImg
+			if displayThumb == "" {
+				displayThumb = thumb
+			}
+
+			content := source
+			if width, ok := itemMap["width"]; ok {
+				w := toString(width)
+				if h, ok2 := itemMap["height"]; ok2 {
+					h2 := toString(h)
+					if w != "" && h2 != "" {
+						content = w + " × " + h2
+						if source != "" {
+							content += " — " + source
+						}
+					}
+				}
+			}
+
+			out = append(out, contracts.MainResult{
+				Template:  "images",
+				Title:     title,
+				Content:   content,
+				URL:       &linkPtr,
+				Thumbnail: displayThumb,
+				Engine:    "qwant_images",
+				Score:     0,
+				Category:  "images",
+				Engines:   []string{"qwant_images"},
+			})
+		}
+	}
+
+	return contracts.SearchResponse{
+		Query:               query,
+		NumberOfResults:    len(out),
+		Results:             out,
+		Answers:             []map[string]any{},
+		Corrections:         []string{},
+		Infoboxes:           []map[string]any{},
+		Suggestions:         []string{},
+		UnresponsiveEngines: [][2]string{},
+	}, nil
+}