DuckDB: Improve SQL management to avoid injection (#44)

[fb64]

Issue

Fixes #44

Change

Use JDBC PreparedStatement instead of raw SQL to avoid injection in DuckDBEmbeddingStore

General checklist

• There are no breaking changes
• I have added unit and integration tests for my change
• I have manually run all the unit tests in all modules, and they are all green
• I have manually run all integration tests in the module I have added/changed, and they are all green

[Martin7-1]

@fb64 Thank you!