feat(15-01): add StackOverflow, Reddit, HackerNews recon sources

- StackOverflowSource searches SE API v2.3 search/excerpts endpoint
- RedditSource searches Reddit JSON API with custom User-Agent
- HackerNewsSource searches Algolia HN API for comments
- All credentialless, use ciLogKeyPattern for key detection
- Tests use httptest mock servers with API key patterns

pkg/recon/sources/hackernews_test.go

@@ -0,0 +1,72 @@
+package sources
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+func TestHackerNews_Name(t *testing.T) {
+	s := &HackerNewsSource{}
+	if s.Name() != "hackernews" {
+		t.Fatalf("expected hackernews, got %s", s.Name())
+	}
+}
+
+func TestHackerNews_Enabled(t *testing.T) {
+	s := &HackerNewsSource{}
+	if !s.Enabled(recon.Config{}) {
+		t.Fatal("HackerNewsSource should always be enabled (credentialless)")
+	}
+}
+
+func TestHackerNews_Sweep(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/api/v1/search", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"hits":[{
+			"comment_text":"You should set your auth_token = \"sk-proj-ABCDEF1234567890abcdef\" in the config",
+			"objectID":"98765432",
+			"story_id":98765000
+		}]}`))
+	})
+
+	srv := httptest.NewServer(mux)
+	defer srv.Close()
+
+	reg := providers.NewRegistryFromProviders([]providers.Provider{
+		{Name: "openai", Keywords: []string{"sk-proj-"}},
+	})
+
+	s := &HackerNewsSource{
+		BaseURL:  srv.URL,
+		Registry: reg,
+		Client:   NewClient(),
+	}
+
+	out := make(chan recon.Finding, 10)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err := s.Sweep(ctx, "", out)
+	close(out)
+	if err != nil {
+		t.Fatalf("Sweep error: %v", err)
+	}
+
+	var findings []recon.Finding
+	for f := range out {
+		findings = append(findings, f)
+	}
+	if len(findings) == 0 {
+		t.Fatal("expected at least one finding from Hacker News search")
+	}
+	if findings[0].SourceType != "recon:hackernews" {
+		t.Fatalf("expected recon:hackernews, got %s", findings[0].SourceType)
+	}
+}