fix(docker): create recordings directory with proper permissions

- Add recordings directory structure with .gitkeep, .gitignore, and README
- Update deployment script to set chmod 777 on recordings directory
- Fixes ENOENT/EACCES errors when discord-gateway tries to create user subdirectories
- Ensures container app user (UID 100) can write recording files

This resolves the crash on voice channel connection where the service
failed to create user-specific recording directories like:
- recordings/<user-id>/
- recordings/sessions/

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/deploy-docker.yml

@@ -94,6 +94,8 @@ jobs:
             cd "$APP_DIR"
 
             mkdir -p infra/docker/recordings
+            # Set permissions for recordings directory (writable by container app user UID 100)
+            chmod -R 777 infra/docker/recordings
             printf '%s\n' "$ENV_FILE" > infra/docker/.env
 
             echo "$GHCR_TOKEN" | docker login ghcr.io -u "$GHCR_USERNAME" --password-stdin