Add custom types, version command, and restore --verify flag

- Add internal/types package with type-safe wrappers for IDs, hashes,
  paths, and credentials (FileID, BlobID, ChunkHash, etc.)
- Implement driver.Valuer and sql.Scanner for UUID-based types
- Add `vaultik version` command showing version, commit, go version
- Add `--verify` flag to restore command that checksums all restored
  files against expected chunk hashes with progress bar
- Remove fetch.go (dead code, functionality in restore)
- Clean up TODO.md, remove completed items
- Update all database and snapshot code to use new custom types

internal/database/database.go

@@ -154,6 +154,11 @@ func (db *DB) Conn() *sql.DB {
 	return db.conn
 }
 
+// Path returns the path to the database file.
+func (db *DB) Path() string {
+	return db.path
+}
+
 // BeginTx starts a new database transaction with the given options.
 // The caller is responsible for committing or rolling back the transaction.
 // For write transactions, consider using the Repositories.WithTx method instead,