feat(17-04): implement notification dispatcher with tests

- NotifyNewFindings sends to all subscribers on scan completion with findings
- NotifyFinding sends real-time individual finding notifications (always masked)
- formatNotification/formatErrorNotification/formatFindingNotification helpers
- Zero findings = no notification; errors get separate error format
- Per-subscriber error handling: log and continue on individual send failures
- 6 tests pass: subscribe DB round-trip, no-subscriber no-op, zero-finding skip,
  message format validation, error format, masked key enforcement

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/bot/notify.go

@@ -0,0 +1,124 @@
+package bot
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/mymmrac/telego"
+	"github.com/mymmrac/telego/telegoutil"
+	"github.com/salvacybersec/keyhunter/pkg/engine"
+	"github.com/salvacybersec/keyhunter/pkg/scheduler"
+)
+
+// NotifyNewFindings sends a notification to all subscribers about scan results.
+// It returns the number of messages successfully sent and any per-subscriber errors.
+// If FindingCount is 0 and Error is nil, no notification is sent (silent success).
+// If Error is non-nil, an error notification is sent instead.
+func (b *Bot) NotifyNewFindings(result scheduler.JobResult) (int, []error) {
+	// No notification for zero-finding success.
+	if result.FindingCount == 0 && result.Error == nil {
+		return 0, nil
+	}
+
+	subs, err := b.cfg.DB.ListSubscribers()
+	if err != nil {
+		log.Printf("notify: listing subscribers: %v", err)
+		return 0, []error{fmt.Errorf("listing subscribers: %w", err)}
+	}
+	if len(subs) == 0 {
+		return 0, nil
+	}
+
+	var msg string
+	if result.Error != nil {
+		msg = formatErrorNotification(result)
+	} else {
+		msg = formatNotification(result)
+	}
+
+	var sent int
+	var errs []error
+	for _, sub := range subs {
+		if b.bot == nil {
+			// No telego bot (test mode) -- count as would-send.
+			continue
+		}
+		params := telegoutil.Message(telego.ChatID{ID: sub.ChatID}, msg)
+		if _, sendErr := b.bot.SendMessage(context.Background(), params); sendErr != nil {
+			log.Printf("notify: sending to chat %d: %v", sub.ChatID, sendErr)
+			errs = append(errs, fmt.Errorf("chat %d: %w", sub.ChatID, sendErr))
+			continue
+		}
+		sent++
+	}
+
+	return sent, errs
+}
+
+// NotifyFinding sends a real-time notification about an individual finding
+// to all subscribers. The key is always masked.
+func (b *Bot) NotifyFinding(finding engine.Finding) (int, []error) {
+	subs, err := b.cfg.DB.ListSubscribers()
+	if err != nil {
+		log.Printf("notify: listing subscribers: %v", err)
+		return 0, []error{fmt.Errorf("listing subscribers: %w", err)}
+	}
+	if len(subs) == 0 {
+		return 0, nil
+	}
+
+	msg := formatFindingNotification(finding)
+
+	var sent int
+	var errs []error
+	for _, sub := range subs {
+		if b.bot == nil {
+			continue
+		}
+		params := telegoutil.Message(telego.ChatID{ID: sub.ChatID}, msg)
+		if _, sendErr := b.bot.SendMessage(context.Background(), params); sendErr != nil {
+			log.Printf("notify: sending finding to chat %d: %v", sub.ChatID, sendErr)
+			errs = append(errs, fmt.Errorf("chat %d: %w", sub.ChatID, sendErr))
+			continue
+		}
+		sent++
+	}
+
+	return sent, errs
+}
+
+// formatNotification builds the notification message for a successful scan
+// with findings.
+func formatNotification(result scheduler.JobResult) string {
+	return fmt.Sprintf(
+		"New findings from scheduled scan!\n\nJob: %s\nNew keys found: %d\nDuration: %s\n\nUse /stats for details.",
+		result.JobName,
+		result.FindingCount,
+		result.Duration,
+	)
+}
+
+// formatErrorNotification builds the notification message for a scan that
+// encountered an error.
+func formatErrorNotification(result scheduler.JobResult) string {
+	return fmt.Sprintf(
+		"Scheduled scan error\n\nJob: %s\nDuration: %s\nError: %v",
+		result.JobName,
+		result.Duration,
+		result.Error,
+	)
+}
+
+// formatFindingNotification builds the notification message for an individual
+// finding. Always uses the masked key.
+func formatFindingNotification(finding engine.Finding) string {
+	return fmt.Sprintf(
+		"New key detected!\nProvider: %s\nKey: %s\nSource: %s:%d\nConfidence: %s",
+		finding.ProviderName,
+		finding.KeyMasked,
+		finding.Source,
+		finding.LineNumber,
+		finding.Confidence,
+	)
+}