feat(11-02): add PastebinSource and GistPasteSource for paste site scanning

- PastebinSource: two-phase search+raw-fetch with keyword matching
- GistPasteSource: scrapes gist.github.com public search (no auth)
- Both implement recon.ReconSource with httptest-based tests

pkg/recon/sources/gistpaste.go

@@ -0,0 +1,152 @@
+package sources
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// GistPasteSource scrapes gist.github.com's public search (no auth required)
+// for API key leaks. This is distinct from Phase 10's GistSource which uses
+// the authenticated GitHub API.
+//
+// Auth: none. Rate: Every(3s), Burst 1.
+type GistPasteSource struct {
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+// gistPasteLinkRE matches gist links: /<user>/<hex-hash>
+var gistPasteLinkRE = regexp.MustCompile(`^/[^/]+/[a-f0-9]+$`)
+
+// Compile-time assertion.
+var _ recon.ReconSource = (*GistPasteSource)(nil)
+
+func (s *GistPasteSource) Name() string          { return "gistpaste" }
+func (s *GistPasteSource) RateLimit() rate.Limit { return rate.Every(3 * time.Second) }
+func (s *GistPasteSource) Burst() int            { return 1 }
+func (s *GistPasteSource) RespectsRobots() bool  { return true }
+
+// Enabled always returns true: gist search scraping requires no credentials.
+func (s *GistPasteSource) Enabled(_ recon.Config) bool { return true }
+
+// Sweep searches gist.github.com for each provider keyword, fetches raw gist
+// content, and emits Findings for keyword matches.
+func (s *GistPasteSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
+	base := s.BaseURL
+	if base == "" {
+		base = "https://gist.github.com"
+	}
+	client := s.Client
+	if client == nil {
+		client = NewClient()
+	}
+
+	queries := BuildQueries(s.Registry, "gistpaste")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	keywords := gistPasteKeywordSet(s.Registry)
+	if len(keywords) == 0 {
+		return nil
+	}
+
+	for _, q := range queries {
+		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
+			}
+		}
+
+		searchURL := fmt.Sprintf("%s/search?q=%s", base, url.QueryEscape(q))
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, searchURL, nil)
+		if err != nil {
+			return fmt.Errorf("gistpaste: build search req: %w", err)
+		}
+		resp, err := client.Do(ctx, req)
+		if err != nil {
+			return fmt.Errorf("gistpaste: search fetch: %w", err)
+		}
+		links, err := extractAnchorHrefs(resp.Body, gistPasteLinkRE)
+		_ = resp.Body.Close()
+		if err != nil {
+			return fmt.Errorf("gistpaste: parse search html: %w", err)
+		}
+
+		for _, gistPath := range links {
+			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
+				}
+			}
+
+			rawURL := fmt.Sprintf("%s%s/raw", base, gistPath)
+			rawReq, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
+			if err != nil {
+				return fmt.Errorf("gistpaste: build raw req: %w", err)
+			}
+			rawResp, err := client.Do(ctx, rawReq)
+			if err != nil {
+				continue // skip this gist on error
+			}
+			body, readErr := io.ReadAll(io.LimitReader(rawResp.Body, 256*1024))
+			_ = rawResp.Body.Close()
+			if readErr != nil {
+				continue
+			}
+
+			content := string(body)
+			for kw, provName := range keywords {
+				if strings.Contains(content, kw) {
+					out <- recon.Finding{
+						ProviderName: provName,
+						Source:       fmt.Sprintf("%s%s", base, gistPath),
+						SourceType:   "recon:gistpaste",
+						Confidence:   "low",
+						DetectedAt:   time.Now(),
+					}
+					break // one finding per gist
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// gistPasteKeywordSet builds keyword->providerName map from registry.
+func gistPasteKeywordSet(reg *providers.Registry) map[string]string {
+	out := make(map[string]string)
+	if reg == nil {
+		return out
+	}
+	for _, p := range reg.List() {
+		for _, k := range p.Keywords {
+			if k == "" {
+				continue
+			}
+			if _, ok := out[k]; !ok {
+				out[k] = p.Name
+			}
+		}
+	}
+	return out
+}