refactor: consolidate blockchain explorer into single app and update backup ignore patterns

- Remove standalone explorer-web app (README, HTML, package files)
- Add /web endpoint to blockchain-explorer for web interface access
- Update .gitignore to exclude application backup archives (*.tar.gz, *.zip)
- Add backup documentation files to .gitignore (BACKUP_INDEX.md, README.md)
- Consolidate explorer functionality into main blockchain-explorer application

.gitignore

@@ -163,6 +163,16 @@ backup/updates/*.tar.gz
 backup/updates/*.zip
 backup/updates/*.tar.bz2
 
+# Application backup archives
+backup/explorer_backup_*.tar.gz
+backup/*_backup_*.tar.gz
+backup/*_backup_*.zip
+
+# Backup documentation and indexes
+backup/BACKUP_INDEX.md
+backup/*.md
+backup/README.md
+
 # ===================
 # Temporary Files
 # ===================