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/resources/views/overlays/desktop.blade.php

@@ -0,0 +1,148 @@
+@extends('layouts.overlay')
+
+@section('title', 'DESKTOP')
+
+@section('body-class', 'camera-hud-body')
+
+@section('styles')
+<style>
+  :root {
+    --cam-x: 1937px; --cam-y: 98px;  --cam-w: 549px;  --cam-h: 309px; --cam-pad: 10px;
+    --scr-x: 10px;   --scr-y: 14px;  --scr-w: 1976px; --scr-h: 1209px; --scr-pad: 0px;
+  }
+  #signal { transform: translateY(-0.10em); }
+</style>
+@endsection
+
+@section('crt')
+{{-- transparent overlay — no CRT overlays --}}
+@endsection
+
+@section('content')
+  @include('partials.screen-frame', ['id' => 'scr', 'label' => 'SCR 01'])
+  @include('partials.camera-frame', ['id' => 'cam', 'label' => 'CAM 01'])
+
+  <footer class="status-bar">
+    <div class="status-line">
+      <div class="live-block">
+        <span class="live-dot"></span>
+        <span>LIVE</span>
+      </div>
+      <span class="sep">·</span>
+      <span class="scene-name">OPHI-118 // DESKTOP</span>
+      <span class="spacer"></span>
+      <span class="hud-tag"><span class="dim">SIGNAL</span><span id="signal" data-profile="normal">▮▮▮▯▯</span></span>
+      <span class="sep">·</span>
+      <span class="hud-tag"><span class="dim">UTC</span><span id="clock">--:--:--</span></span>
+    </div>
+    <div class="status-line meta-line">
+      <span class="icon">◷</span>
+      <span class="elapsed" id="elapsed">00:00:00</span>
+      <span class="sep">·</span>
+      <span class="icon" title="microphone">🎙</span>
+      <span style="color: var(--term-fg);">ON</span>
+    </div>
+  </footer>
+@endsection
+
+@section('scripts')
+<script>
+  'use strict';
+  const pad = HUD.pad;
+
+  const streamStart = Date.now();
+  function tickElapsed() {
+    const s = Math.floor((Date.now() - streamStart) / 1000);
+    const h = Math.floor(s / 3600);
+    const mm = Math.floor((s / 60) % 60);
+    const ss = s % 60;
+    document.getElementById('elapsed').textContent = `${pad(h)}:${pad(mm)}:${pad(ss)}`;
+  }
+  tickElapsed(); setInterval(tickElapsed, 1000);
+
+  const params       = new URLSearchParams(location.search);
+  const CAM_SOURCE   = params.get('camera') || 'Camera';
+  const SCR_SOURCE   = params.get('screen') || 'Screen Capture (PipeWire)';
+  const SCENE_LOCK   = params.get('scene')  || null;
+
+  const camEl    = document.getElementById('cam');
+  const scrEl    = document.getElementById('scr');
+  const rootStyle = document.documentElement.style;
+
+  function renderedSize(t) {
+    const useBounds = t.boundsType
+                    && t.boundsType !== 'OBS_BOUNDS_NONE'
+                    && (t.boundsWidth ?? 0) > 0;
+    if (useBounds) return { w: t.boundsWidth, h: t.boundsHeight };
+    return {
+      w: (t.sourceWidth  ?? 0) * (t.scaleX ?? 1),
+      h: (t.sourceHeight ?? 0) * (t.scaleY ?? 1),
+    };
+  }
+
+  function makeFrame(obs, sourceName, frameEl, varPrefix) {
+    const state = { sceneName: null, itemId: null };
+    const setVisible = (v) => frameEl.classList.toggle('off', !v);
+    const setTransform = (t) => {
+      if (!t) return;
+      const { w, h } = renderedSize(t);
+      if (!(w > 0 && h > 0)) return;
+      rootStyle.setProperty(`--${varPrefix}-x`, `${t.positionX}px`);
+      rootStyle.setProperty(`--${varPrefix}-y`, `${t.positionY}px`);
+      rootStyle.setProperty(`--${varPrefix}-w`, `${w}px`);
+      rootStyle.setProperty(`--${varPrefix}-h`, `${h}px`);
+    };
+    return {
+      async rebind(sceneName) {
+        state.sceneName = sceneName;
+        state.itemId    = null;
+        if (!sceneName) { setVisible(false); return; }
+        try {
+          const r = await obs.call('GetSceneItemId', { sceneName, sourceName });
+          state.itemId = r.sceneItemId;
+          const e = await obs.call('GetSceneItemEnabled', { sceneName, sceneItemId: state.itemId });
+          setVisible(e.sceneItemEnabled);
+          const t = await obs.call('GetSceneItemTransform', { sceneName, sceneItemId: state.itemId });
+          setTransform(t.sceneItemTransform);
+        } catch {
+          setVisible(false);
+        }
+      },
+      handleEvent(d) {
+        if (d.eventData?.sceneName    !== state.sceneName
+         || d.eventData?.sceneItemId !== state.itemId) return;
+        if (d.eventType === 'SceneItemEnableStateChanged') {
+          setVisible(d.eventData.sceneItemEnabled);
+        } else if (d.eventType === 'SceneItemTransformChanged') {
+          setTransform(d.eventData.sceneItemTransform);
+        }
+      },
+    };
+  }
+
+  OBSWSBootstrap.connect({
+    onConnect: async (obs) => {
+      const camFrame = makeFrame(obs, CAM_SOURCE, camEl, 'cam');
+      const scrFrame = makeFrame(obs, SCR_SOURCE, scrEl, 'scr');
+      let scene = SCENE_LOCK;
+      if (!scene) {
+        try {
+          const r = await obs.call('GetCurrentProgramScene');
+          scene = r.currentProgramSceneName || r.sceneName || null;
+        } catch { /* leave null */ }
+      }
+      await Promise.all([camFrame.rebind(scene), scrFrame.rebind(scene)]);
+      obs.addEventListener('event', async (ev) => {
+        const d = ev.detail || {};
+        if (!SCENE_LOCK && d.eventType === 'CurrentProgramSceneChanged') {
+          const next = d.eventData?.sceneName;
+          await Promise.all([camFrame.rebind(next), scrFrame.rebind(next)]);
+          return;
+        }
+        camFrame.handleEvent(d);
+        scrFrame.handleEvent(d);
+      });
+    },
+  });
+</script>
+@endsection