chore(powersync): align rusqlite with sqlx-sqlite

[birdmanmandbir]

Summary

Align the Rust SDK's rusqlite dependency with stable sqlx-sqlite by moving from rusqlite 0.39 to 0.32.

This keeps the SDK on libsqlite3-sys 0.30.1, which lets downstream crates use the current stable sqlx-sqlite 0.8.6 in the same Cargo graph without hitting Cargo's single-links = "sqlite3" conflict.

Details

• Downgrades rusqlite in the SDK, test utilities, and egui example.
• Replaces Statement::query_one calls with query_row, which is the equivalent API available on rusqlite 0.32.
• Updates rustls-webpki to 0.103.13 because the repo pre-push cargo deny hook blocks the existing vulnerable 0.103.9 lockfile entry.

Validation

• cargo fmt --check
• cargo test -p powersync
• pre-push hook:
  • clippy
  • cargo deny check