[flthibaud]

tsqueryExpr appended :* to the text form of websearch_to_tsquery. A query ending with a negated hyphenated word (chat -foo-bar, -e-mail) renders with a closing parenthesis, and ):* is not valid tsquery syntax, so the search returned a 500.

• The prefix marker is now appended only when the rendered text ends with a lexeme (a closing quote); otherwise the text is cast as it is.
• New DB test TestSearchWithTrailingNegatedHyphenatedWord; TestSearchMatchesAPrefix still passes.

Tested with gofmt, go vet ./... and go test -race ./... against a migrated postgres:16 (no test skipped).

Closes #18

[flthibaud]

Review: OK to merge.

• Code and DB test by Mistral. Its change broke TestSearchQueryExpr (it counted the config name twice, now four times); I corrected that assertion.
• Checked on PostgreSQL that a phrase query still ends with a quote, so "foo bar" keeps its prefix match.
• All three acceptance points of Search returns 500 when the query ends with a negated hyphenated word #18 are covered except the HTTP-level one, which follows from the model test.