ci: add RPM packaging for cortex and neuron

- cortex.spec: gateway binary, cortex.service systemd unit,
  cortex.toml + models.toml config files
- neuron.spec: neuron binary, neuron.service systemd unit,
  neuron.toml config file
- Parallel CI: srpm-cortex and srpm-neuron jobs build SRPMs
  concurrently, then publish to separate COPR repos
  (helexa/cortex and helexa/neuron)
- Shared cortex user/group across both packages
- Example configs: cortex.example.toml, neuron.example.toml,
  models.example.toml

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

data/cortex.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=Cortex — inference gateway for multi-node GPU clusters
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/cortex serve --config /etc/cortex/cortex.toml
+Restart=on-failure
+RestartSec=5
+User=cortex
+Group=cortex
+
+[Install]
+WantedBy=multi-user.target