ci: add Gitea CI, RPM spec, license, and repo hygiene

- Add .gitea/workflows/ci.yml with fmt/clippy/test on all branches
  and SRPM build + COPR publish on version tags
- Add cortex.spec for Fedora RPM packaging
- Add GPL-3.0-or-later LICENSE file
- Add cortex.example.toml with generic hostnames; gitignore cortex.toml
- Scrub infrastructure-specific hostnames from README.md, CLAUDE.md,
  and doc comments
- Fix unused imports and clippy warnings to pass -D warnings
- Fix missing deps (bytes, reqwest, serde_json) exposed during build
- Run cargo fmt across workspace
- Update SPDX license identifier to GPL-3.0-or-later

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

crates/cortex-gateway/src/metrics.rs

@@ -34,18 +34,12 @@ pub fn install(listen: &str) -> Result<()> {
         "cortex_tokens_per_second",
         "Generation throughput in tokens per second"
     );
-    metrics::describe_counter!(
-        "cortex_requests_total",
-        "Total number of proxied requests"
-    );
+    metrics::describe_counter!("cortex_requests_total", "Total number of proxied requests");
     metrics::describe_counter!(
         "cortex_request_errors_total",
         "Total number of failed proxy requests"
     );
-    metrics::describe_counter!(
-        "cortex_evictions_total",
-        "Total number of model evictions"
-    );
+    metrics::describe_counter!("cortex_evictions_total", "Total number of model evictions");
     metrics::describe_counter!(
         "cortex_cold_starts_total",
         "Total number of cold-start model loads"