Code Quality Improvements: SQLite Wrapper Enhancements

[alienx5499]

Summary

This PR improves code quality by adding const correctness, better error handling, and additional utility methods to the SQLite wrapper class.

Changes

• include/libp2p/storage/sqlite.hpp: Enhanced method declarations with const correctness and better documentation
• src/storage/sqlite.cpp: Improved implementations with better error handling and new utility methods

Methods Updated

• getErrorCode() - Returns SQLite extended error code (const)
• getErrorMessage() - Returns human-readable error message (const)
• countChanges() - Returns number of rows modified (const)
• getDatabaseFile() - Returns database file path (const, new)
• getStatementCount() - Returns number of prepared statements (const, new)
• getStatement() - Improved error messages with detailed handle information
• execCommand() - Better error handling and documentation
• execQuery() - Better error handling and documentation

Benefits

• Better API Design: Methods that don't modify state are properly marked as const
• Improved Error Handling: More descriptive error messages and proper exception handling
• Enhanced Debugging: New utility methods for database file path and statement count
• Code Clarity: Better documentation and more informative error messages
• C++ Best Practices: Follows modern C++ const correctness and exception safety guidelines
• Better Exception Safety: Proper re-throwing of programming errors vs runtime errors

Testing

• No breaking changes - all improvements are additive
• Existing functionality remains unchanged
• New utility methods provide additional debugging capabilities
• Improved error messages help with troubleshooting

[alienx5499]

@turuslan Could you please review this PR when you get a chance?