Add exclude patterns, snapshot prune, and other improvements

- Implement exclude patterns with anchored pattern support:
  - Patterns starting with / only match from root of source dir
  - Unanchored patterns match anywhere in path
  - Support for glob patterns (*.log, .*, **/*.pack)
  - Directory patterns skip entire subtrees
  - Add gobwas/glob dependency for pattern matching
  - Add 16 comprehensive tests for exclude functionality

- Add snapshot prune command to clean orphaned data:
  - Removes incomplete snapshots from database
  - Cleans orphaned files, chunks, and blobs
  - Runs automatically at backup start for consistency

- Add snapshot remove command for deleting snapshots

- Add VAULTIK_AGE_SECRET_KEY environment variable support

- Fix duplicate fx module provider in restore command

- Change snapshot ID format to hostname_YYYY-MM-DDTHH:MM:SSZ

internal/snapshot/module.go

@@ -38,6 +38,7 @@ func provideScannerFactory(cfg *config.Config, repos *database.Repositories, sto
 			CompressionLevel: cfg.CompressionLevel,
 			AgeRecipients:    cfg.AgeRecipients,
 			EnableProgress:   params.EnableProgress,
+			Exclude:          cfg.Exclude,
 		})
 	}
 }