refactor(A1): remove Flamenco, simplify render pipeline to Celery-only

- Remove flamenco-manager and flamenco-worker from docker-compose.yml
- Delete flamenco_client.py, flamenco_tasks.py, docker_scaler.py
- Simplify render_dispatcher.py to Celery-only (removes ~300 lines)
- Remove Flamenco beat schedule from celery_app.py
- Clean admin.py: remove flamenco settings, endpoints, threejs validation
- Clean orders.py cancel-render: Celery revoke only
- Clean worker.py: remove flamenco_job_id from activity response
- Migration 032: cancel lingering flamenco jobs, remove flamenco settings
- PLAN.md: mark all decisions confirmed, status IN UMSETZUNG

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

.gitignore

@@ -5,3 +5,39 @@ node_modules/
 *.log
 core
 /blender-renderer/core
+
+# Python cache
+__pycache__/
+*.py[cod]
+*.pyo
+
+# Node / Vite build output
+dist/
+node_modules/
+
+# Celery beat schedule
+celerybeat-schedule
+celerybeat.pid
+
+# Test cache
+.pytest_cache/
+.coverage
+
+# IDE
+.vscode/
+.idea/
+
+# Excel lock files
+~$*
+.~lock.*#
+
+# Kundendaten ausschließen
+*.stp
+*.step
+*.stl
+*.xls
++.xslx
+*.csv
+*.xlsx
+
+*.blend1