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>

controller/README.md

@@ -145,6 +145,21 @@ The app catalog lives in a separate Git repository. The controller:
 5. Pre-generated secret values are submitted as hidden form inputs so the **same values** the user saw are saved to `app.yaml` (no silent re-generation on submit). Controller saves `app.yaml`, sets in-memory `Deployed` + `Deploying` flags, then runs `docker compose up -d` **asynchronously** in a goroutine — API returns immediately so the UI switches to the progress panel without waiting for image pulls. On failure the goroutine reverts both disk and in-memory state and sets `DeployError`.
 6. 3-step progress panel polls `GET /api/stacks/{name}` every 3s: config saved → `deploying` (pulling images) → containers starting → health check passed. New `StateDeploying` state shown while compose-up is in progress (no containers yet).
 7. Post-deploy: locked fields (DB_PASSWORD, etc.) become read-only; the "Automatikusan generált értékek" section continues to show the saved values on the settings page
+8. The deploy/settings page includes **start/stop/restart** buttons for deployed apps, plus a "Megnyitás ↗" link to the app's subdomain URL (only visible when running)
+
+#### Catch-All Page for Stopped Apps
+
+When a user visits a stopped or undeployed app's subdomain (e.g., `travel.demo-felhom.eu`), the controller serves a branded error page instead of Traefik's raw 404:
+
+- **Traefik catch-all router**: The controller's `docker-compose.yml` registers a second router (`catchall`) with `priority=1` (lowest) and `HostRegexp(.+)`. Running apps always win; only requests with no matching container reach the controller.
+- **`CatchAllMiddleware`** in `server.go` intercepts requests where `Host` ≠ `felhom.DOMAIN`, serves the catch-all page **without auth** (user has no session on the app subdomain).
+- **`findStackBySubdomain()`** identifies the app by matching the subdomain against deployed `app.yaml` `SUBDOMAIN` env or metadata fallback.
+- **`catchall.html`** — standalone template (no layout, inline CSS) showing the app name, status ("leállítva" / "nincs telepítve" / "nem található"), and links to the controller dashboard or the app's detail page.
+- **Subdomain links** on the Alkalmazások page are only shown for deployed apps (non-deployed apps have no guaranteed subdomain yet).
+
+#### Dashboard "Megnyitás" Button
+
+Running apps on the Vezérlőpult now show a "Megnyitás ↗" button that opens the app's subdomain in a new tab. The `Subdomains` map is built in `dashboardHandler` from `app.yaml` env or metadata fallback.
 
 #### App Info Pages
 
@@ -1132,7 +1147,7 @@ controller/
 │   │   └── templates/              # 7 wizard HTML templates (Hungarian)
 │   ├── recovery/info.go            # Recovery info file generator (recovery-info.txt)
 │   └── web/
-│       ├── server.go               # HTTP server, routing, static files, executeTemplate wrapper
+│       ├── server.go               # HTTP server, routing, static files, catch-all middleware, executeTemplate wrapper
 │       ├── auth.go                 # Session auth + per-session CSRF token, login/logout, session cleanup
 │       ├── csrf.go                 # CsrfProtect middleware, csrfToken/csrfField helpers
 │       ├── handlers.go             # Page handlers (dashboard, stacks, deploy, backups, etc.)
@@ -1143,7 +1158,7 @@ controller/
 │       ├── alerts.go               # State-based alert generation
 │       ├── funcmap.go              # Template functions (state colors, Hungarian formatting)
 │       ├── embed.go                # go:embed for templates + Chart.js
-│       └── templates/              # 14 HTML files + style.css (Hungarian UI, incl. debug.html)
+│       └── templates/              # 15 HTML files + style.css (Hungarian UI, incl. debug.html, catchall.html)
 ├── configs/
 │   ├── controller.yaml.example     # Full config reference
 │   └── example-felhom-metadata.yml # .felhom.yml format reference