webapp: introduce Laravel app under webapp/ for scene overlays

Replaces the per-scene HTML directories (landing/, loading/, game/,
desktop/, goodbye/, music-box/, music/) with a single Laravel app
serving every overlay over HTTP. Supervisord runs `php artisan serve`
on 127.0.0.1:1118 and the OBS scene JSON now references HTTP routes
instead of file:// URLs.

Highlights:
 - public/css/hud.css consolidates the duplicated HUD chrome,
   scanlines/vignette/flicker, terminal styling, and pulse keyframes
   that were copy-pasted across all seven scenes.
 - Blade partials own hud-strip, crt-overlays, obs-ws-scripts,
   camera-frame, screen-frame; the seven scenes extend a shared
   overlay layout.
 - Artisan commands (`rig:setup`, `rig:telemetry`, `rig:loading`,
   `rig:playlist`, `rig:cmd`) replace the shell scripts that wrote
   per-rig JSON snapshots. TwitchHelix + HardwareSnapshot services
   handle the work the bash + Python helpers used to.
 - ObsWsClient + MusicCommandController kill the 250 ms cmd.js poll
   in the music daemon: POST /cmd/{skip|prev|pause|resume} opens a
   short-lived Pawl WS, authenticates, and broadcasts mpd:cmd.
 - AudioController streams files from the configured music dirs so
   CEF can load tracks under the HTTP origin (Chromium blocks
   HTTP-origin pages from loading file:// media).
 - DataController serves /data/playlist.js (with ETag mtime cache)
   and /cover.jpg (no-store) so the existing overlays' window.__PLAYLIST
   and cover.jpg cache-bust pattern keeps working.

scripts/obs-webapp.supervisord.conf is the supervisord unit; install
to /etc/supervisor.d/obs-webapp.conf.
scripts/rewrite-scene-urls.py is a one-shot tool that rewrites
basic/scenes/Default_Stream_HUD.json from file:// to HTTP URLs.
basic/scenes/Default_Stream_HUD.json.pre-webapp is the rollback
artifact (made with OBS closed; full pre-migration state).

The seven old scene directories, vendor/, and the bash scripts are
still on disk pending visual verification; the next commit will
prune them.

webapp/config/services.php

@@ -0,0 +1,38 @@
+<?php
+
+return [
+
+    /*
+    |--------------------------------------------------------------------------
+    | Third Party Services
+    |--------------------------------------------------------------------------
+    |
+    | This file is for storing the credentials for third party services such
+    | as Mailgun, Postmark, AWS and more. This file provides the de facto
+    | location for this type of information, allowing packages to have
+    | a conventional file to locate the various service credentials.
+    |
+    */
+
+    'postmark' => [
+        'key' => env('POSTMARK_API_KEY'),
+    ],
+
+    'resend' => [
+        'key' => env('RESEND_API_KEY'),
+    ],
+
+    'ses' => [
+        'key' => env('AWS_ACCESS_KEY_ID'),
+        'secret' => env('AWS_SECRET_ACCESS_KEY'),
+        'region' => env('AWS_DEFAULT_REGION', 'us-east-1'),
+    ],
+
+    'slack' => [
+        'notifications' => [
+            'bot_user_oauth_token' => env('SLACK_BOT_USER_OAUTH_TOKEN'),
+            'channel' => env('SLACK_BOT_USER_DEFAULT_CHANNEL'),
+        ],
+    ],
+
+];