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/swagger.go

@@ -0,0 +1,118 @@
+package sources
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"regexp"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// SwaggerSource probes for publicly accessible Swagger/OpenAPI documentation
+// endpoints. Developers frequently include real API keys in "example" and
+// "default" fields of security scheme definitions or parameter specifications.
+type SwaggerSource struct {
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+var _ recon.ReconSource = (*SwaggerSource)(nil)
+
+func (s *SwaggerSource) Name() string              { return "swagger" }
+func (s *SwaggerSource) RateLimit() rate.Limit      { return rate.Every(3 * time.Second) }
+func (s *SwaggerSource) Burst() int                 { return 2 }
+func (s *SwaggerSource) RespectsRobots() bool       { return true }
+func (s *SwaggerSource) Enabled(_ recon.Config) bool { return true }
+
+// swaggerDocPaths are common locations for Swagger/OpenAPI documentation.
+var swaggerDocPaths = []string{
+	"/swagger.json",
+	"/openapi.json",
+	"/api-docs",
+	"/v2/api-docs",
+	"/swagger/v1/swagger.json",
+	"/docs/openapi.json",
+}
+
+// swaggerKeyPattern matches potential API keys in example/default fields of
+// Swagger JSON. It looks for "example" or "default" keys with string values
+// that look like API keys (16+ alphanumeric characters).
+var swaggerKeyPattern = regexp.MustCompile(`"(?:example|default)"\s*:\s*"([a-zA-Z0-9_\-]{16,})"`)
+
+func (s *SwaggerSource) 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, "swagger")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	for _, q := range queries {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		for _, path := range swaggerDocPaths {
+			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
+			}
+			req.Header.Set("Accept", "application/json")
+
+			resp, err := client.Do(ctx, req)
+			if err != nil {
+				continue
+			}
+
+			// Try to parse as JSON to verify it's a valid Swagger doc.
+			var doc map[string]interface{}
+			if err := json.NewDecoder(resp.Body).Decode(&doc); err != nil {
+				_ = resp.Body.Close()
+				continue
+			}
+			_ = resp.Body.Close()
+
+			// Re-marshal to search for example/default fields with key patterns.
+			raw, err := json.Marshal(doc)
+			if err != nil {
+				continue
+			}
+
+			if swaggerKeyPattern.Match(raw) {
+				out <- recon.Finding{
+					ProviderName: q,
+					Source:       probeURL,
+					SourceType:   "recon:swagger",
+					Confidence:   "medium",
+					DetectedAt:   time.Now(),
+				}
+			}
+		}
+	}
+	return nil
+}