Fix bd-666: Replace N+1 query pattern in auto-import with batch fetch

- Batch fetch all existing issues with SearchIssues() upfront
- Use O(1) map lookup instead of O(n) GetIssue() calls
- Improves performance dramatically with 1000+ issues
- All tests pass

analyze_duplicates.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# Analyze duplicate issues
+
+echo "# Duplicate Issues Report"
+echo ""
+echo "Generated: $(date)"
+echo ""
+
+./bd list --json | jq -r 'group_by(.title) | .[] | select(length > 1) | {
+  title: .[0].title,
+  count: length,
+  issues: [.[] | {id, status, created_at}]
+} | "## \(.title)\nCount: \(.count)\n" + (.issues | map("- \(.id) (\(.status)) created \(.created_at)") | join("\n")) + "\n"'