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>

1 files changed, 8 insertions, 1 deletions

diff --git a/packages/meshbay-client/package.json b/packages/meshbay-client/package.json
index 61d75d7..b9c5a50 100644
--- a/packages/meshbay-client/package.json
+++ b/packages/meshbay-client/package.json
@@ -1,7 +1,7 @@
 {
   "name": "meshbay-client",
   "version": "0.1.0",
-  "description": "MeshBay desktop client \u2014 the interface ships with the application, not from the hub",
+  "description": "MeshBay desktop client — the interface ships with the application, not from the hub",
   "license": "AGPL-3.0-or-later",
   "main": "src/main.js",
   "private": true,
@@ -39,5 +39,12 @@
         "python3-meshbay-common"
       ]
     }
+  },
+  "dependencies": {
+    "bonjour-service": "^1.4.4",
+    "castv2-client": "^1.2.0"
+  },
+  "overrides": {
+    "protobufjs": "^7.5.5"
   }
 }