polish(web): favicon, Punktfunk casing, display-save toast, idle stop button

- Favicon: the brand-mark lens SVG at /favicon.svg, linked from the root head.
- Branding: user-facing "punktfunk" → "Punktfunk" (tab title, app_name,
  pairing prose, the logo aria-labels/SVG titles) — protocol identifiers
  (punktfunk/1, _punktfunk._udp, binary/module names) stay lowercase.
- The display policy auto-saves on every preset pick / field edit with no
  signal; mount @unom/ui's sonner Toaster in the root and fire a success toast
  from the save funnel's onSuccess (new i18n key, en + de). First toast usage
  in the console — errors stay inline as before.
- The stop-session button rendered destructive-red even with nothing to stop:
  variant switches to the muted `secondary` while no session is active.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/messages/en.json

@@ -1,7 +1,8 @@
 {
 	"$schema": "https://inlang.com/schema/inlang-message-format",
-	"app_name": "punktfunk",
+	"app_name": "Punktfunk",
 	"app_tagline": "management console",
+	"display_settings_saved": "Display configuration saved",
 	"nav_dashboard": "Dashboard",
 	"nav_host": "Host",
 	"nav_displays": "Virtual displays",
@@ -128,8 +129,8 @@
 	"pairing_success": "Paired successfully.",
 	"pairing_failed": "Pairing failed — check the PIN and try again.",
 	"pairing_native_title": "Pair a device",
-	"pairing_native_desc": "Show a one-time PIN here, then enter it in your punktfunk app to pair this device.",
-	"pairing_native_disabled": "The native host isn't running. Start it with `serve --native` to pair punktfunk devices.",
+	"pairing_native_desc": "Show a one-time PIN here, then enter it in your Punktfunk app to pair this device.",
+	"pairing_native_disabled": "The native host isn't running. Start it with `serve --native` to pair Punktfunk devices.",
 	"pairing_native_arm": "Pair a device",
 	"pairing_native_enter": "Enter this PIN on your device:",
 	"pairing_native_expires": "Expires in",