feat(web): move Virtual displays to its own nav section; roomier preset grid

The Host page was crowded (identity, codecs, ports, GPU, displays, compositors) and the
virtual-display config surface is large enough to warrant its own home.

- New **Virtual displays** nav section: `/displays` route + `sections/Displays` (moved
  DisplayCard out of `sections/Host`), a `MonitorPlay` sidebar entry after Host, and
  `nav_displays` i18n. Removed the displays card from the Host page/view.
- On its own page the card splits into two: **Configuration** (presets + custom axes) and
  **Live displays** (the live list + arrangement table) — room to breathe.
- Presets now render in a max-2-column grid (`sm:grid-cols-2`) with larger padding, a bigger
  section heading + preset titles (text-base semibold), roomier spacing, and bottom-aligned
  "what it sets" badges so the cards line up.

web tsc + vite build + biome-lint green; deployed + verified on the Mutter box (.21).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/messages/de.json

@@ -4,6 +4,7 @@
 	"app_tagline": "Verwaltungskonsole",
 	"nav_dashboard": "Übersicht",
 	"nav_host": "Host",
+	"nav_displays": "Virtuelle Anzeigen",
 	"nav_clients": "Gekoppelte Geräte",
 	"nav_pairing": "Kopplung",
 	"nav_library": "Bibliothek",
@@ -49,6 +50,7 @@
 	"gpu_env_note": "PUNKTFUNK_RENDER_ADAPTER={value} bindet die GPU im Automatikmodus.",
 	"host_displays": "Virtuelle Displays",
 	"host_displays_help": "Wie virtuelle Displays erstellt, aktiv gehalten und angeordnet werden. Wähle eine Voreinstellung oder „Benutzerdefiniert“, um Optionen direkt zu setzen. Eine Änderung gilt ab der nächsten Sitzung.",
+	"display_config_title": "Konfiguration",
 	"display_preset": "Voreinstellung",
 	"display_preset_custom": "Benutzerdefiniert",
 	"display_preset_default": "Standard",