reduce production image size without runtime drift

backend/.dockerignore

@@ -0,0 +1,32 @@
+.git
+.github
+.devcontainer
+.env
+__pycache__/
+*.py[cod]
+*.log
+*.sqlite3
+.coverage
+.pytest_cache/
+.mypy_cache/
+.ruff_cache/
+coverage.xml
+htmlcov/
+server/.pytest_cache
+server/.mypy_cache
+server/.ruff_cache
+server/.coverage
+server/coverage.xml
+server/htmlcov
+server/.hypothesis
+server/scheduler.log
+server/**/*.log
+server/tests/
+server/**/tests/
+server/test_*.py
+server/**/__pycache__/
+server/**/*.py[cod]
+server/media/
+server/staticfiles/
+server/.env
+server/.env.*