perf(list): optimize bd list --json to fetch only needed dependencies (#1316)

Add GetDependencyRecordsForIssues method to storage interface that
fetches dependencies only for specified issue IDs instead of all
dependencies in the database.

This optimizes bd list --json which previously called
GetAllDependencyRecords() even when displaying only a few issues
(e.g., bd list --limit 10).

- Add GetDependencyRecordsForIssues to Storage interface
- Implement in SQLite, Dolt, and Memory backends
- Update list.go JSON output to use targeted method
- Update mock storage in tests

Origin: Mayor's review of PR #1296

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/list.go

@@ -1194,7 +1194,7 @@ var listCmd = &cobra.Command{
 			}
 			labelsMap, _ := store.GetLabelsForIssues(ctx, issueIDs)
 			depCounts, _ := store.GetDependencyCounts(ctx, issueIDs)
-			allDeps, _ := store.GetAllDependencyRecords(ctx)
+			allDeps, _ := store.GetDependencyRecordsForIssues(ctx, issueIDs)
 
 			// Populate labels and dependencies for JSON output
 			for _, issue := range issues {