fix: Migrate from mattn/go-sqlite3 to modernc.org/sqlite

[nfebe]

Replace CGo-based SQLite driver with pure-Go implementation to fix cross-compilation builds. The release workflow produces binaries with CGO_ENABLED=0 which caused go-sqlite3 to register as a stub, breaking auth, traffic, scheduler, security, audit, and cluster databases.

Bump version to 0.1.55.

[sourceant]

Code Review Summary

This PR migrates the SQLite driver from the CGO-dependent mattn/go-sqlite3 to the pure-Go modernc.org/sqlite. This facilitates easier cross-compilation and static linking.

🚀 Key Improvements

• Removed CGO dependency for database access.
• Fixed build issues in environments where CGO_ENABLED=0.
• Standardized SQLite connection strings using _pragma parameters.

💡 Minor Suggestions

• Add _mutex=full to connection strings for additional thread safety.
• Centralize database connection logic to reduce code duplication.

[sourceant]

Review complete. No specific code suggestions were generated. See the overview comment for a summary.