fix(search): sanitize FTS5 query input

[Ricky-7-Yan]

Summary

Fixes #160.

• Sanitize raw FTS5 query input before tokenization
• Strip FTS5 operators such as AND, OR, NOT, and NEAR/5
• Strip FTS5 control syntax such as quotes, parentheses, wildcard, and column markers
• Keep normal keyword search behavior by preserving sanitized tokens
• Add tests for regex fallback and jieba tokenization paths

Tests

• npx.cmd vitest run src/core/store/sqlite.test.ts
• npx.cmd vitest run

[Ricky-7-Yan]

Superseded by #374 with a clearer PR template and task checklist.