chore(release): v0.2.8 — multiple managed local models

- The gateway can now run several local .cmf models at once: a [[cmf.servers]]
  list, one supervised `cortiq serve` per entry on its own port, each registered
  in the pool and independently routable/pinnable. The single legacy
  local_model/local_port still works (back-compat via effective_servers()).
- Settings → Local models is now a rows editor (id · path · port + check · threads
  · GPU) with add/remove and per-server serving status.
- Deleting a managed model stops just its server and removes its file — unless
  another model still points at the same file (shared-file guard).

Cargo.lock

@@ -285,7 +285,7 @@ checksum = "1d07550c9036bf2ae0c684c4297d503f838287c83c53686d05370d0e139ae570"
 
 [[package]]
 name = "cortiq-gateway"
-version = "0.2.7"
+version = "0.2.8"
 dependencies = [
  "anyhow",
  "arc-swap",