feat: Add batch deletion support (bd-127)

- Add DeleteIssues() method in sqlite.go for atomic batch deletion
- Support multiple issue IDs as arguments or from file
- Add --from-file flag to read IDs from file (supports comments)
- Add --dry-run mode for safe preview without deleting
- Add --cascade flag for recursive deletion of dependents
- Add --force flag to orphan dependents instead of failing
- Pre-collect connected issues before deletion for text reference updates
- Add orphan deduplication to prevent duplicate IDs
- Add rows.Err() checks in all row iteration loops
- Full transaction safety - all deletions succeed or none do
- Comprehensive statistics tracking (deleted, dependencies, labels, events)
- Update README and CHANGELOG with batch deletion docs

Fixed critical code review issues:
- Dry-run mode now properly uses dryRun parameter instead of deleting data
- Text references are pre-collected before deletion so they update correctly
- Added orphan deduplication and error checks
- Updated defer rollback pattern per Go best practices

CHANGELOG.md

@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- **Batch Deletion**: Enhanced `bd delete` command with batch operations (bd-127)
+  - Delete multiple issues at once: `bd delete bd-1 bd-2 bd-3 --force`
+  - Read from file: `bd delete --from-file deletions.txt --force`
+  - Dry-run mode: `--dry-run` to preview deletions before execution
+  - Cascade mode: `--cascade` to recursively delete all dependents
+  - Force mode: `--force` to orphan dependents instead of failing
+  - Atomic transactions: all deletions succeed or none do
+  - Comprehensive statistics: tracks deleted issues, dependencies, labels, and events
+
 ## [0.9.9] - 2025-10-17
 
 ### Added