fix(tauri): resolve target-dir from Cargo config in dev script

The dev-with-daemon script hardcoded `target/debug` as the daemon
binary path, which breaks when a custom target-dir is configured
in .cargo/config.toml or CARGO_TARGET_DIR. Use `cargo metadata` to
resolve the actual target directory, with fallback to the default.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>