build: bump Rust version to 1.94.0

[velocitysystems]

Summary

Bumps the project's Rust version to 1.94.0 to match the updated Silvermine standard (silvermine/silvermine-info#47), plus committed example lockfiles for reproducible builds.

Toolchain bump

• rust-toolchain.toml channel → 1.94.0
• rust-version in the workspace Cargo.toml and all three crates (sqlx-sqlite-conn-mgr, sqlx-sqlite-observer, sqlx-sqlite-toolkit)
• rust-version in both example apps (observer-demo, pagination-demo)
• README requirement note (1.77.2 → 1.94.0)
• CI workflow toolchain (.github/workflows/ci.yml)

Example app lockfiles

Without a committed lockfile, a fresh resolve of the example apps pulls bitflags 2.12.0, which overflows the macro recursion limit in dispatch2 and breaks the build. This stops ignoring examples/**/Cargo.lock and commits a coherent lockfile (pinning bitflags 2.11.0) for both example apps, matching the approach already used by the audio and connectivity example apps.

Verification

• npm run standards passes (markdownlint, clippy, fmt, commitlint, node check) — no new 1.94.0 lints.
• The plugin, all three crates, and both example apps compile cleanly under 1.94.0.