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>

models.example.toml

@@ -0,0 +1,29 @@
+# models.example.toml — model catalogue
+#
+# Copy to /etc/cortex/models.toml and adjust for your environment.
+# Describes how to serve each model. Cortex matches these profiles
+# against discovered neuron topologies for placement decisions.
+
+[[models]]
+id = "your-org/large-model"
+harness = "mistralrs"
+quant = "Q4_K_M"
+vram_mb = 19000
+min_devices = 2
+min_device_vram_mb = 10000
+pinned_on = ["gpu-large"]
+
+[[models]]
+id = "your-org/medium-model"
+harness = "mistralrs"
+quant = "Q6_K"
+vram_mb = 12000
+min_devices = 1
+pinned_on = ["gpu-medium"]
+
+[[models]]
+id = "your-org/embedding-model"
+harness = "mistralrs"
+quant = "Q8_0"
+vram_mb = 8000
+min_devices = 1