chore(release): v0.2.6 — Settings UX, empty pool by default, CMF port check

- Settings: "?" help tooltips on every option; router key auto-probes the
  connection right after saving (no more hanging "unavailable")
- Local models card reworked into 3 clear steps (install cortiq → add model →
  run locally); removed the hand-entered .cmf path / pool-id fields — models
  are added via the Import tab and the managed server registers them
- Fresh install ships an EMPTY model pool; the local .cmf is auto-registered by
  the managed CMF server, so it needs no static [[models]] entry
- New: port-availability check — GET /admin/api/cmf/port + "Check port" button
  with next-free-port suggestion. bind()+connect() probe so Docker-proxied /
  dual-stack ports (e.g. 8081) are correctly detected as occupied
- /admin/api/cmf now reports the serving model + port; card shows "▶ serving …"
- On-demand runtime install: POST /admin/api/cmf/install

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cortiq-gateway"
-version = "0.2.5"
+version = "0.2.6"
 edition = "2021"
 rust-version = "1.75"
 license = "Apache-2.0"