Package the systemd fan curve solution as an RPM and publish via Fedora COPR

Package the BC-250 systemd-based fan-curve solution as an installable RPM and publish it through Fedora COPR.

This should build on #1 once the fan-control script/service is stable.

## Goals
- Ship the fan-control script and systemd unit as a Fedora RPM.
- Install files into appropriate system locations with correct ownership and permissions.
- Enable straightforward installation and upgrades through DNF.
- Publish builds through a Fedora COPR project.
- Keep the package focused on the BC-250 fan-control solution rather than broader system configuration.

## Packaging work
- Add an RPM spec file.
- Package the fan-curve executable/script.
- Package the systemd service unit.
- Add appropriate runtime dependencies.
- Add `%post` / systemd packaging macros as appropriate so systemd reloads correctly after install/upgrade.
- Do not automatically start the service during package installation unless there is a strong reason to do so.
- Document install, enable/start, upgrade, and uninstall commands.

## COPR
- Create/configure a COPR project for the package.
- Build for the Fedora releases we actually use/support.
- Verify installation using the COPR repository and `dnf` rather than a locally built RPM.

## Acceptance criteria
- `dnf install` from the COPR installs the script and systemd unit cleanly.
- `systemctl enable --now` starts the fan curve successfully on a BC-250.
- The service survives reboot and restarts after unexpected failure.
- hwmon device discovery from #1 works when installed from the RPM.
- Upgrade and removal leave systemd in a clean state.
- README/PROJECT documentation contains the COPR installation instructions.

Start by reviewing issue #1 and the existing fan-control script and systemd service once that work is stable. Add the RPM spec and package the executable and unit, then configure the Fedora COPR project. Verify installation, enable/start, reboot recovery, upgrade, removal, and documentation through COPR and dnf on a BC-250.

Written by the indexing model from the issue text.