feat: catch-all page for stopped apps, deploy controls, dashboard open button

Stopped/undeployed app subdomains now show a branded page instead of
Traefik 404. Deploy settings page gains start/stop/restart controls.
Dashboard shows "Megnyitás" button for running apps.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,17 @@
 ## Changelog
 
+### v0.28.3 — Catch-All Page, Deploy Controls, Dashboard Open (2026-02-23)
+
+#### Added
+- **Catch-all page for stopped/undeployed apps** — When a user visits a stopped app's subdomain (e.g., `travel.demo-felhom.eu`), they now see a branded felhom page with the app name and status ("Az alkalmazás jelenleg le van állítva") instead of Traefik's raw 404. Implemented via a low-priority (1) Traefik catch-all router on the controller container + `CatchAllMiddleware` in `server.go` that intercepts non-controller hosts and renders standalone `catchall.html` without auth.
+- **Start/Stop/Restart buttons on deploy settings page** — Deployed apps now show Indítás/Leállítás/Újraindítás buttons in the page header, plus a "Megnyitás ↗" link to the app's subdomain (visible when running). Previously the deploy page had no state controls.
+- **"Megnyitás ↗" button on Vezérlőpult** — Running apps on the dashboard now show an open button that launches the app in a new tab. Uses the `Subdomains` map built from `app.yaml` SUBDOMAIN env with metadata fallback.
+- **`findStackBySubdomain()`** helper in `server.go` — looks up stacks by subdomain, checking deployed `app.yaml` env first, then `.felhom.yml` metadata.
+
+#### Changed
+- **Subdomain links on Alkalmazások page** — Links now only shown for deployed apps (previously shown for all apps including non-deployed ones where the subdomain isn't final yet).
+- **`docker-compose.yml`** — Added 6 catch-all Traefik router labels (`traefik.http.routers.catchall.*`) with `priority=1` and `certresolver=letsencrypt`.
+
 ### v0.28.2 — Async Deploy & AdventureLog Fix (2026-02-23)
 
 #### Changed