fix: add shared volume between worker containers for temp files

The main worker and ffmpeg-worker run in separate containers with
isolated filesystems. Add a shared volume mounted at /shared-tmp
and set TMPDIR so Python's tempfile module uses it. This allows
ffmpeg-worker to access video files created by the main worker.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -158,6 +158,8 @@ services:
       redis:
         condition: service_healthy
     environment:
+      # Shared temp directory for ffmpeg operations
+      TMPDIR: /shared-tmp
       # App configuration
       APP_ENV: ${APP_ENV:-dev}
 
@@ -208,6 +210,7 @@ services:
     volumes:
       - ./secrets:/secrets:ro
       - worker-logs:/app/logs
+      - shared-tmp:/shared-tmp
     networks:
       - accessible-video-network
     logging:
@@ -233,6 +236,8 @@ services:
       redis:
         condition: service_healthy
     environment:
+      # Shared temp directory for ffmpeg operations
+      TMPDIR: /shared-tmp
       # App configuration
       APP_ENV: ${APP_ENV:-dev}
 
@@ -283,6 +288,7 @@ services:
     volumes:
       - ./secrets:/secrets:ro
       - ffmpeg-worker-logs:/app/logs
+      - shared-tmp:/shared-tmp
     networks:
       - accessible-video-network
     logging:
@@ -315,3 +321,5 @@ volumes:
     name: accessible-video-worker-logs
   ffmpeg-worker-logs:
     name: accessible-video-ffmpeg-worker-logs
+  shared-tmp:
+    name: accessible-video-shared-tmp