feat(14-03): implement SwaggerSource and DeployPreviewSource with tests

- SwaggerSource probes OpenAPI doc endpoints for API keys in example/default fields
- DeployPreviewSource scans Vercel/Netlify preview URLs for __NEXT_DATA__ env leaks
- Both implement ReconSource, credentialless, with httptest-based tests

pkg/recon/sources/deploypreview.go

@@ -0,0 +1,107 @@
+package sources
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"regexp"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// DeployPreviewSource scans Vercel and Netlify deploy preview URLs for leaked
+// API keys. Deploy previews frequently use different (less restrictive)
+// environment variables than production, and their URLs are often guessable
+// from PR numbers or commit hashes.
+type DeployPreviewSource struct {
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+var _ recon.ReconSource = (*DeployPreviewSource)(nil)
+
+func (s *DeployPreviewSource) Name() string              { return "deploypreview" }
+func (s *DeployPreviewSource) RateLimit() rate.Limit      { return rate.Every(3 * time.Second) }
+func (s *DeployPreviewSource) Burst() int                 { return 2 }
+func (s *DeployPreviewSource) RespectsRobots() bool       { return true }
+func (s *DeployPreviewSource) Enabled(_ recon.Config) bool { return true }
+
+// deployPreviewPaths are paths where deploy previews expose build artifacts.
+var deployPreviewPaths = []string{
+	"/",
+	"/_next/data/",
+	"/static/js/main.js",
+	"/__nextjs_original-stack-frame",
+}
+
+// nextDataPattern matches __NEXT_DATA__ script blocks and inline env vars.
+var nextDataPattern = regexp.MustCompile(`(?i)(__NEXT_DATA__|NEXT_PUBLIC_|REACT_APP_|VITE_)[A-Z_]*(API[_]?KEY|SECRET|TOKEN)?['":\s]*[=:,]\s*['"]([a-zA-Z0-9_\-]{8,})['"]`)
+
+func (s *DeployPreviewSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
+	base := s.BaseURL
+	if base == "" {
+		return nil
+	}
+	client := s.Client
+	if client == nil {
+		client = NewClient()
+	}
+
+	queries := BuildQueries(s.Registry, "deploypreview")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	for _, q := range queries {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		for _, path := range deployPreviewPaths {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+
+			if s.Limiters != nil {
+				if err := s.Limiters.Wait(ctx, s.Name(), s.RateLimit(), s.Burst(), false); err != nil {
+					return err
+				}
+			}
+
+			probeURL := base + path
+			req, err := http.NewRequestWithContext(ctx, http.MethodGet, probeURL, nil)
+			if err != nil {
+				continue
+			}
+
+			resp, err := client.Do(ctx, req)
+			if err != nil {
+				continue
+			}
+
+			body, err := io.ReadAll(io.LimitReader(resp.Body, 512*1024))
+			_ = resp.Body.Close()
+			if err != nil {
+				continue
+			}
+
+			if nextDataPattern.Match(body) {
+				out <- recon.Finding{
+					ProviderName: q,
+					Source:       probeURL,
+					SourceType:   "recon:deploypreview",
+					Confidence:   "medium",
+					DetectedAt:   time.Now(),
+				}
+				break // one finding per query is sufficient
+			}
+		}
+	}
+	return nil
+}