Fix Docker build: add ext-zip, clean cache, fix DB_DATABASE default

- Add php zip extension to Dockerfile (required by ZipArchive)
- Remove bootstrap/cache/*.php during build to prevent stale
  dev-only service providers (e.g. BoostServiceProvider) from loading
- Default DB_DATABASE to /app/database/database.sqlite in
  docker-compose.yml so env() fallback works correctly

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

docker-compose.yml

@@ -23,7 +23,7 @@ services:
       DB_CONNECTION: ${DB_CONNECTION:-sqlite}
       DB_HOST: ${DB_HOST:-}
       DB_PORT: ${DB_PORT:-}
-      DB_DATABASE: ${DB_DATABASE:-}
+      DB_DATABASE: ${DB_DATABASE:-/app/database/database.sqlite}
       DB_USERNAME: ${DB_USERNAME:-}
       DB_PASSWORD: ${DB_PASSWORD:-}
       LOG_CHANNEL: ${LOG_CHANNEL:-stderr}
@@ -63,7 +63,7 @@ services:
       DB_CONNECTION: ${DB_CONNECTION:-sqlite}
       DB_HOST: ${DB_HOST:-}
       DB_PORT: ${DB_PORT:-}
-      DB_DATABASE: ${DB_DATABASE:-}
+      DB_DATABASE: ${DB_DATABASE:-/app/database/database.sqlite}
       DB_USERNAME: ${DB_USERNAME:-}
       DB_PASSWORD: ${DB_PASSWORD:-}
       LOG_CHANNEL: ${LOG_CHANNEL:-stderr}