fix(prefs): persist favicon choice and apply to HTML results

- Save favicon cookie on POST /preferences; reflect selection in template
- Add getFaviconService helper; pass favicon service into FromResponse
- Compute ResultView.FaviconIconURL (none/google/duckduckgo/self proxy)
- Update result_item and video_item templates; add httpapi/views tests

Made-with: Cursor

internal/httpapi/httpapi_test.go

@@ -32,17 +32,17 @@ import (
 // mockUpstreamHandler returns controlled JSON responses.
 func mockUpstreamJSON(query string) contracts.SearchResponse {
 	return contracts.SearchResponse{
-		Query:            query,
-		NumberOfResults:  2,
+		Query:           query,
+		NumberOfResults: 2,
 		Results: []contracts.MainResult{
 			{Title: "Upstream Result 1", URL: ptr("https://upstream.example/1"), Content: "From upstream", Engine: "upstream"},
 			{Title: "Upstream Result 2", URL: ptr("https://upstream.example/2"), Content: "From upstream", Engine: "upstream"},
 		},
-		Answers:              []map[string]any{},
-		Corrections:          []string{},
-		Infoboxes:            []map[string]any{},
-		Suggestions:          []string{"upstream suggestion"},
-		UnresponsiveEngines:  [][2]string{},
+		Answers:             []map[string]any{},
+		Corrections:         []string{},
+		Infoboxes:           []map[string]any{},
+		Suggestions:         []string{"upstream suggestion"},
+		UnresponsiveEngines: [][2]string{},
 	}
 }
 
@@ -74,6 +74,7 @@ func newTestServer(t *testing.T) (*httptest.Server, *httpapi.Handler) {
 	mux.HandleFunc("/", h.Index)
 	mux.HandleFunc("/search", h.Search)
 	mux.HandleFunc("/autocompleter", h.Autocompleter)
+	mux.HandleFunc("/preferences", h.Preferences)
 
 	server := httptest.NewServer(mux)
 	t.Cleanup(server.Close)
@@ -228,3 +229,50 @@ func TestSearch_SourceURLInFooter(t *testing.T) {
 		t.Error("expected AGPLv3 link in footer")
 	}
 }
+
+func TestPreferences_PostSetsFaviconCookie(t *testing.T) {
+	server, _ := newTestServer(t)
+	client := &http.Client{CheckRedirect: func(*http.Request, []*http.Request) error {
+		return http.ErrUseLastResponse
+	}}
+	req, _ := http.NewRequest(http.MethodPost, server.URL+"/preferences", strings.NewReader("favicon=google&theme=dark"))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("request failed: %v", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusFound {
+		t.Fatalf("expected redirect 302, got %d", resp.StatusCode)
+	}
+	found := false
+	for _, c := range resp.Cookies() {
+		if c.Name == "favicon" {
+			found = true
+			if c.Value != "google" {
+				t.Fatalf("expected favicon cookie google, got %q", c.Value)
+			}
+		}
+	}
+	if !found {
+		t.Fatal("expected favicon cookie to be set")
+	}
+}
+
+func TestPreferences_GetReflectsFaviconCookie(t *testing.T) {
+	server, _ := newTestServer(t)
+	req, _ := http.NewRequest(http.MethodGet, server.URL+"/preferences", nil)
+	req.AddCookie(&http.Cookie{Name: "favicon", Value: "duckduckgo"})
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("request failed: %v", err)
+	}
+	defer resp.Body.Close()
+
+	body, _ := io.ReadAll(resp.Body)
+	html := string(body)
+	if !strings.Contains(html, `option value="duckduckgo" selected`) {
+		t.Fatalf("expected duckduckgo option selected, body: %s", html)
+	}
+}