chore(dev): add .python-version and requirements_dev.txt

.python-version pins the local interpreter to 3.13. requirements_dev.txt
collects the lint/format/type/security/spell tooling plus prek; it pulls in
requirements_test.txt but deliberately does not pin pillow/numpy (they
conflict with the Home Assistant pin used by the test stack).

Author: foXaCe

.python-version

@@ -0,0 +1 @@
+3.13

requirements_dev.txt

@@ -0,0 +1,20 @@
+# Developer tooling for the Dreame Vacuum integration.
+#
+# Runtime dependencies live in custom_components/dreame_vacuum/manifest.json and
+# are installed by Home Assistant. Do NOT pin pillow/numpy here: their pins
+# conflict with the Home Assistant version pulled in by
+# pytest-homeassistant-custom-component. For local mypy, install the runtime
+# libraries separately:
+#   pip install pillow numpy pybase64 requests pycryptodome python-miio mini-racer paho-mqtt
+-r requirements_test.txt
+
+# Lint, format, type-check, security, spelling
+ruff
+mypy
+types-requests
+bandit[toml]
+codespell
+pip-audit
+
+# Pre-commit hook runner (Rust drop-in for pre-commit)
+prek