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.

scripts/obs-webapp.supervisord.conf

@@ -0,0 +1,31 @@
+; supervisord program file for the OPHI-118 scene overlay webapp.
+;
+; Listens on 127.0.0.1:1118 (CH 118.0 in the overlay lore, easy to remember).
+;
+; Install:
+;   sudo install -m 644 scripts/obs-webapp.supervisord.conf /etc/supervisor.d/obs-webapp.conf
+;   sudo supervisorctl reread && sudo supervisorctl update
+;
+; Restart after config / route / env changes:
+;   sudo supervisorctl restart obs-webapp
+;
+; Logs:
+;   tail -F webapp/storage/logs/supervisord.{out,err}.log
+
+[program:obs-webapp]
+command=/usr/bin/php artisan serve --host=127.0.0.1 --port=1118
+directory=/home/jin/.config/obs-studio/webapp
+user=jin
+environment=HOME="/home/jin",USER="jin",PATH="/usr/local/sbin:/usr/local/bin:/usr/bin"
+autostart=true
+autorestart=true
+startsecs=2
+startretries=3
+stopwaitsecs=10
+stopsignal=TERM
+stdout_logfile=/home/jin/.config/obs-studio/webapp/storage/logs/supervisord.out.log
+stderr_logfile=/home/jin/.config/obs-studio/webapp/storage/logs/supervisord.err.log
+stdout_logfile_maxbytes=10MB
+stdout_logfile_backups=3
+stderr_logfile_maxbytes=10MB
+stderr_logfile_backups=3

scripts/rewrite-scene-urls.py

@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+"""Rewrite OBS browser_source URLs in a scene-collection JSON from `file://` to
+`http://127.0.0.1:1118/`.
+
+Usage:
+    python3 scripts/rewrite-scene-urls.py basic/scenes/Default_Stream_HUD.json
+
+Idempotent: runs against a partially-converted file are no-ops.
+
+Also moves the landing/static-hum.wav ffmpeg_source path to its new home under
+webapp/public/audio/.
+
+OBS MUST be closed when this runs — OBS rewrites scene files on exit.
+"""
+import json
+import re
+import sys
+
+
+BROWSER_MAPPING = {
+    'landing/index.html':           'http://127.0.0.1:1118/landing',
+    'loading/index.html':           'http://127.0.0.1:1118/loading',
+    'game/index.html':              'http://127.0.0.1:1118/game',
+    'desktop/index.html':           'http://127.0.0.1:1118/desktop',
+    'goodbye/index.html':           'http://127.0.0.1:1118/goodbye',
+    'music/index.html':             'http://127.0.0.1:1118/music-daemon',
+    'music-box/index.html':         'http://127.0.0.1:1118/music-box',
+    'music-box/widget.html':        'http://127.0.0.1:1118/music-box/widget',
+    'music-box/cover.html':         'http://127.0.0.1:1118/music-box/cover',
+    'music-box/nc-music-box.html':  'http://127.0.0.1:1118/music-box/nc',
+}
+
+AUDIO_OLD = 'landing/static-hum.wav'
+AUDIO_NEW = 'webapp/public/audio/static-hum.wav'
+
+
+def rewrite_browser_source(src):
+    s = src.get('settings', {})
+    for old, new in BROWSER_MAPPING.items():
+        for k in ('url', 'local_file'):
+            v = s.get(k, '')
+            if old in v:
+                # Preserve query strings (e.g. ?bars=0).
+                m = re.search(r'\?[^"\s]*$', v)
+                qs = m.group(0) if m else ''
+                s['url'] = new + qs
+                s.pop('local_file', None)
+                s['is_local_file'] = False
+                return True
+    return False
+
+
+def rewrite_audio_source(src):
+    s = src.get('settings', {})
+    lf = s.get('local_file', '')
+    if lf.endswith(AUDIO_OLD):
+        s['local_file'] = lf.replace(AUDIO_OLD, AUDIO_NEW)
+        return True
+    return False
+
+
+def main():
+    if len(sys.argv) != 2:
+        print(__doc__, file=sys.stderr)
+        return 2
+    path = sys.argv[1]
+    doc = json.load(open(path))
+    rewrites = 0
+    for src in doc.get('sources', []):
+        sid = src.get('id', '')
+        if sid == 'browser_source':
+            if rewrite_browser_source(src):
+                rewrites += 1
+        elif sid == 'ffmpeg_source':
+            if rewrite_audio_source(src):
+                rewrites += 1
+    json.dump(doc, open(path, 'w'), indent=4, ensure_ascii=False)
+    print(f'wrote {path} ({rewrites} sources rewritten)')
+
+
+if __name__ == '__main__':
+    sys.exit(main() or 0)