feat(repository): add streamed RDF import/export and functional transactions

[remiceres]

Important: Please review and merge the Storage PR (#629) first before this PR. This branch is based on top of #629.

Summary

This PR enriches the public Repository API with direct RDF loading and exporting capabilities, introduces functional transaction helpers (inTransaction / computeInTransaction), and implements progressive line-by-line parsing for N-Triples and N-Quads to bound input memory on large datasets.

Key Changes

• Direct RDF Import (load): Adds overloaded load() methods on Repository and RepositoryConnection accepting Path, InputStream, or Reader, with automatic format detection via file extension.
• Progressive Streaming Parsers: Implements LineRDFParser for N-Triples and N-Quads, reusing ANTLR lexer/parser across lines so temporary memory is bounded by line size rather than document size.
• Functional Transactions: Adds inTransaction(Consumer) and computeInTransaction(Function) with automatic commit and rollback, capturing secondary rollback failures via addSuppressed.
• Direct RDF Export (export): Adds safe export to Path, OutputStream, or Writer, preventing silent data loss by rejecting named graphs when targeting formats that only support default graphs (e.g. Turtle).
• Validation: 3,178 unit tests passing (100%), 0 SonarLint issues on all modified/new Java files, reference memory at 600k statements unchanged (90,827,088 bytes).