fix(store): sanitize local search FTS queries

[upsetbit]

Summary

Fixes #294.

This PR hardens local FTS search query handling so malformed or punctuation-heavy user queries no longer surface raw SQLite/FTS5 errors.

What changed

• Quote literal FTS5 terms before passing them to MATCH.
• Preserve supported operators only when they appear in a valid operator position.
• Treat punctuation such as hyphens and ordinary parentheses as literal search text unless it is part of supported NEAR (...) syntax.
• Wrap remaining FTS parser failures as invalid search query ... instead of leaking SQL logic error / fts5: internals.
• Add regression tests for hyphenated identifiers, dangling operators, punctuation, prefix search, OR, and wrapped invalid NEAR syntax.

Validation

• go test ./internal/store -run Search -count=1
• go test ./internal/store/... -race
• go test ./internal/cli/... -race
• go build -o ./bin/prosa ./cmd/prosa
• Manual repro checks for (, foo(bar), audit OR, NOT audit, and invalid NEAR (audit profile, ) against a synthetic local store.