feat: PostgreSQL extension for Icelandic full-text search

[jokull]

Summary

• C extension embedding lemma-is binary for native PostgreSQL FTS
• icelandic_lexize(), icelandic_fts_lemmas(), icelandic_fts_query(), icelandic_tsvector() functions
• Docker setup for dev/testing
• Integration tests verifying parity with JS implementation

Usage

CREATE EXTENSION icelandic_fts;

-- Lemmatize a word
SELECT icelandic_lexize('hestinum');  -- {hestur}

-- Build tsvector for indexing
SELECT icelandic_tsvector('Börnin fóru í bíó');

-- Search with lemma expansion
SELECT * FROM documents 
WHERE search_vector @@ to_tsquery('simple', icelandic_fts_query('hestur'));

Test plan

• pnpm test tests/pg-extension.integration.test.ts passes
• Manual testing with real corpus

🤖 Generated with Claude Code