feat: LAN Wi-Fi casting to Chromecast via local HTTP relay

Re-serve decrypted fMP4 video over HTTP on the LAN so a Chromecast can
play the stream. The relay runs in the Electron main process — same trust
boundary as downloads and MSE playback.

- cast-relay.js: HTTP server with BoxAccumulator (reassembles WebRTC
  chunks into moof+mdat pairs), ring buffer, backpressure, finish() for
  clean end-of-stream, fixed port range 19550-19553
- cast-chromecast.js: mDNS discovery (bonjour-service) + CASTV2 protocol
  (castv2-client), connect/reload/disconnect lifecycle
- Seek-aware: relay restarts on every seek, Chromecast reloads new URL;
  generation counter prevents stale async errors from killing active
  restarts; landingPlayheadRef suppresses programmatic seeking events
- Device picker in video top bar with scan, device selection, copy-URL
  fallback, and cast status indicator
- IPC bridge (main/preload/platform) for start/push/stop/finish/status/
  discover/chromecastConnect/chromecastReload/chromecastDisconnect
- Phase 3 design doc for DLNA/Smart TV in docs/cast-smart-tv.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

10 files changed, 80 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
index ec56f03..e309834 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transport nicht verbunden',
   'video.err_mse': 'Codec wird für das Streaming nicht unterstützt: {codec}',
 
+  // LAN-Cast
+  'cast.start': 'Auf Gerät übertragen',
+  'cast.stop': 'Übertragung beenden',
+  'cast.copy_url': 'Stream-URL kopieren',
+  'cast.copied': 'URL kopiert',
+  'cast.scanning': 'Suche nach Geräten…',
+  'cast.no_devices': 'Keine Geräte gefunden',
+
   // Settings
   'settings.title': 'Einstellungen',
   'settings.coming_soon': 'Demnächst verfügbar.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
index a8392c7..9a5058e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
@@ -152,6 +152,14 @@ export default {
   'video.err_transport': 'Transport not connected',
   'video.err_mse': 'Codec not supported for streaming: {codec}',
 
+  // LAN cast
+  'cast.start': 'Cast to device',
+  'cast.stop': 'Stop casting',
+  'cast.copy_url': 'Copy stream URL',
+  'cast.copied': 'URL copied',
+  'cast.scanning': 'Scanning for devices…',
+  'cast.no_devices': 'No devices found',
+
   // Settings
   'settings.title': 'Settings',
   'settings.coming_soon': 'Coming soon.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
index 5afb3c3..5a95347 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
@@ -152,6 +152,14 @@ export default {
   'video.err_transport': 'Transporte no conectado',
   'video.err_mse': 'Códec no compatible con la reproducción en continuo: {codec}',
 
+  // LAN cast
+  'cast.start': 'Enviar a dispositivo',
+  'cast.stop': 'Detener envío',
+  'cast.copy_url': 'Copiar URL del stream',
+  'cast.copied': 'URL copiada',
+  'cast.scanning': 'Buscando dispositivos…',
+  'cast.no_devices': 'No se encontraron dispositivos',
+
   // Settings
   'settings.title': 'Ajustes',
   'settings.coming_soon': 'Próximamente.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
index 9eb2f30..4139fc9 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
@@ -153,6 +153,14 @@ export default {
   'video.err_transport': 'Transport non connecté',
   'video.err_mse': 'Codec non pris en charge pour la diffusion : {codec}',
 
+  // LAN cast
+  'cast.start': 'Diffuser sur un appareil',
+  'cast.stop': 'Arrêter la diffusion',
+  'cast.copy_url': "Copier l'URL du flux",
+  'cast.copied': 'URL copiée',
+  'cast.scanning': "Recherche d'appareils…",
+  'cast.no_devices': 'Aucun appareil trouvé',
+
   // Settings
   'settings.title': 'Paramètres',
   'settings.coming_soon': 'Bientôt disponible.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
index 5653ec0..531c8f7 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
@@ -153,6 +153,14 @@ export default {
   'video.err_transport': 'Trasporto non connesso',
   'video.err_mse': 'Codec non supportato per lo streaming: {codec}',
 
+  // LAN cast
+  'cast.start': 'Trasmetti al dispositivo',
+  'cast.stop': 'Interrompi trasmissione',
+  'cast.copy_url': 'Copia URL dello stream',
+  'cast.copied': 'URL copiato',
+  'cast.scanning': 'Ricerca dispositivi…',
+  'cast.no_devices': 'Nessun dispositivo trovato',
+
   // Settings
   'settings.title': 'Impostazioni',
   'settings.coming_soon': 'Prossimamente.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
index aa3899d..1a68827 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
@@ -150,6 +150,14 @@ export default {
   'video.err_transport': 'トランスポートが接続されていません',
   'video.err_mse': 'ストリーミング再生に対応していないコーデックです：{codec}',
 
+  // LAN cast
+  'cast.start': 'デバイスにキャスト',
+  'cast.stop': 'キャストを停止',
+  'cast.copy_url': 'ストリームURLをコピー',
+  'cast.copied': 'URLをコピーしました',
+  'cast.scanning': 'デバイスを検索中…',
+  'cast.no_devices': 'デバイスが見つかりません',
+
   // Settings
   'settings.title': '設定',
   'settings.coming_soon': '近日公開。',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
index c5841dd..d0c9649 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transport niet verbonden',
   'video.err_mse': 'Codec wordt niet ondersteund voor streamen: {codec}',
 
+  // LAN cast
+  'cast.start': 'Naar apparaat casten',
+  'cast.stop': 'Casten stoppen',
+  'cast.copy_url': 'Stream-URL kopiëren',
+  'cast.copied': 'URL gekopieerd',
+  'cast.scanning': 'Apparaten zoeken…',
+  'cast.no_devices': 'Geen apparaten gevonden',
+
   // Settings
   'settings.title': 'Instellingen',
   'settings.coming_soon': 'Binnenkort beschikbaar.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
index eec144b..630548b 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
@@ -159,6 +159,14 @@ export default {
   'video.err_transport': 'Transport nie jest połączony',
   'video.err_mse': 'Kodek nieobsługiwany przy odtwarzaniu strumieniowym: {codec}',
 
+  // LAN cast
+  'cast.start': 'Przesyłaj na urządzenie',
+  'cast.stop': 'Zatrzymaj przesyłanie',
+  'cast.copy_url': 'Kopiuj URL strumienia',
+  'cast.copied': 'URL skopiowany',
+  'cast.scanning': 'Wyszukiwanie urządzeń…',
+  'cast.no_devices': 'Nie znaleziono urządzeń',
+
   // Settings
   'settings.title': 'Ustawienia',
   'settings.coming_soon': 'Wkrótce.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
index ce2adf2..9a6809a 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transporte não conectado',
   'video.err_mse': 'Codec sem suporte para transmissão: {codec}',
 
+  // LAN cast
+  'cast.start': 'Transmitir para dispositivo',
+  'cast.stop': 'Parar transmissão',
+  'cast.copy_url': 'Copiar URL do stream',
+  'cast.copied': 'URL copiada',
+  'cast.scanning': 'Procurando dispositivos…',
+  'cast.no_devices': 'Nenhum dispositivo encontrado',
+
   // Settings
   'settings.title': 'Configurações',
   'settings.coming_soon': 'Em breve.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
index f249835..549b77e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
@@ -147,6 +147,14 @@ export default {
   'video.err_transport': '传输未连接',
   'video.err_mse': '该编解码器不支持流式播放：{codec}',
 
+  // LAN cast
+  'cast.start': '投射到设备',
+  'cast.stop': '停止投射',
+  'cast.copy_url': '复制流媒体链接',
+  'cast.copied': '链接已复制',
+  'cast.scanning': '正在搜索设备…',
+  'cast.no_devices': '未找到设备',
+
   // Settings
   'settings.title': '设置',
   'settings.coming_soon': '即将推出。',