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/pastebin.go

@@ -0,0 +1,156 @@
+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"
+)
+
+// PastebinSource scrapes pastebin.com search results for API key leaks.
+//
+// Two-phase approach per keyword:
+//   - Phase A: search pastebin for keyword, extract paste IDs from result links
+//   - Phase B: fetch raw paste content, keyword-match against provider registry
+//
+// Auth: none (credential-free). Rate: Every(3s), Burst 1 (conservative scraping).
+type PastebinSource struct {
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+// pastebinIDRE matches Pastebin paste links: /XXXXXXXX (8 alphanumeric chars).
+var pastebinIDRE = regexp.MustCompile(`^/[A-Za-z0-9]{8}$`)
+
+// Compile-time assertion.
+var _ recon.ReconSource = (*PastebinSource)(nil)
+
+func (s *PastebinSource) Name() string          { return "pastebin" }
+func (s *PastebinSource) RateLimit() rate.Limit { return rate.Every(3 * time.Second) }
+func (s *PastebinSource) Burst() int            { return 1 }
+func (s *PastebinSource) RespectsRobots() bool  { return true }
+
+// Enabled always returns true: Pastebin scraping requires no credentials.
+func (s *PastebinSource) Enabled(_ recon.Config) bool { return true }
+
+// Sweep searches Pastebin for each provider keyword and scans raw paste content.
+func (s *PastebinSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
+	base := s.BaseURL
+	if base == "" {
+		base = "https://pastebin.com"
+	}
+	client := s.Client
+	if client == nil {
+		client = NewClient()
+	}
+
+	queries := BuildQueries(s.Registry, "pastebin")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	keywords := pastebinKeywordSet(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
+			}
+		}
+
+		// Phase A: search for paste links.
+		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("pastebin: build search req: %w", err)
+		}
+		resp, err := client.Do(ctx, req)
+		if err != nil {
+			return fmt.Errorf("pastebin: search fetch: %w", err)
+		}
+		ids, err := extractAnchorHrefs(resp.Body, pastebinIDRE)
+		_ = resp.Body.Close()
+		if err != nil {
+			return fmt.Errorf("pastebin: parse search html: %w", err)
+		}
+
+		// Phase B: fetch raw content and keyword-match.
+		for _, idPath := range ids {
+			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/raw%s", base, idPath)
+			rawReq, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
+			if err != nil {
+				return fmt.Errorf("pastebin: build raw req: %w", err)
+			}
+			rawResp, err := client.Do(ctx, rawReq)
+			if err != nil {
+				// Skip this paste on fetch error, continue to next.
+				continue
+			}
+			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, idPath),
+						SourceType:   "recon:pastebin",
+						Confidence:   "low",
+						DetectedAt:   time.Now(),
+					}
+					break // one finding per paste
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// pastebinKeywordSet builds keyword->providerName map from registry.
+func pastebinKeywordSet(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
+}