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/app.php

@@ -0,0 +1,126 @@
+<?php
+
+return [
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application Name
+    |--------------------------------------------------------------------------
+    |
+    | This value is the name of your application, which will be used when the
+    | framework needs to place the application's name in a notification or
+    | other UI elements where an application name needs to be displayed.
+    |
+    */
+
+    'name' => env('APP_NAME', 'Laravel'),
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application Environment
+    |--------------------------------------------------------------------------
+    |
+    | This value determines the "environment" your application is currently
+    | running in. This may determine how you prefer to configure various
+    | services the application utilizes. Set this in your ".env" file.
+    |
+    */
+
+    'env' => env('APP_ENV', 'production'),
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application Debug Mode
+    |--------------------------------------------------------------------------
+    |
+    | When your application is in debug mode, detailed error messages with
+    | stack traces will be shown on every error that occurs within your
+    | application. If disabled, a simple generic error page is shown.
+    |
+    */
+
+    'debug' => (bool) env('APP_DEBUG', false),
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application URL
+    |--------------------------------------------------------------------------
+    |
+    | This URL is used by the console to properly generate URLs when using
+    | the Artisan command line tool. You should set this to the root of
+    | the application so that it's available within Artisan commands.
+    |
+    */
+
+    'url' => env('APP_URL', 'http://localhost'),
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application Timezone
+    |--------------------------------------------------------------------------
+    |
+    | Here you may specify the default timezone for your application, which
+    | will be used by the PHP date and date-time functions. The timezone
+    | is set to "UTC" by default as it is suitable for most use cases.
+    |
+    */
+
+    'timezone' => 'UTC',
+
+    /*
+    |--------------------------------------------------------------------------
+    | Application Locale Configuration
+    |--------------------------------------------------------------------------
+    |
+    | The application locale determines the default locale that will be used
+    | by Laravel's translation / localization methods. This option can be
+    | set to any locale for which you plan to have translation strings.
+    |
+    */
+
+    'locale' => env('APP_LOCALE', 'en'),
+
+    'fallback_locale' => env('APP_FALLBACK_LOCALE', 'en'),
+
+    'faker_locale' => env('APP_FAKER_LOCALE', 'en_US'),
+
+    /*
+    |--------------------------------------------------------------------------
+    | Encryption Key
+    |--------------------------------------------------------------------------
+    |
+    | This key is utilized by Laravel's encryption services and should be set
+    | to a random, 32 character string to ensure that all encrypted values
+    | are secure. You should do this prior to deploying the application.
+    |
+    */
+
+    'cipher' => 'AES-256-CBC',
+
+    'key' => env('APP_KEY'),
+
+    'previous_keys' => [
+        ...array_filter(
+            explode(',', (string) env('APP_PREVIOUS_KEYS', ''))
+        ),
+    ],
+
+    /*
+    |--------------------------------------------------------------------------
+    | Maintenance Mode Driver
+    |--------------------------------------------------------------------------
+    |
+    | These configuration options determine the driver used to determine and
+    | manage Laravel's "maintenance mode" status. The "cache" driver will
+    | allow maintenance mode to be controlled across multiple machines.
+    |
+    | Supported drivers: "file", "cache"
+    |
+    */
+
+    'maintenance' => [
+        'driver' => env('APP_MAINTENANCE_DRIVER', 'file'),
+        'store' => env('APP_MAINTENANCE_STORE', 'database'),
+    ],
+
+];