This change extends the C bindings to include transaction support, enabling client SDKs that rely on the C FFI layer to begin, commit, and roll back transactions

What’s included:

• libsql_tx_begin - start a transaction with a configurable behavior
• libsql_tx_commit - commit the transaction
• libsql_tx_rollback - roll back the transaction
• libsql_tx_free - release the transaction handle without implicit commit/rollback

Other changes:

• Updatedtypes.rs to define the transaction wrapper and handle type
• Updatedexample.c

Linked issues:
Closes#2168
Helps address SDK issuelibsql-client-dotnet/issues/21