Implement story 1.1: project scaffold and verified entry points

Creates the complete src/planemapper/ layout with all module stubs,
provisioning and renderer subpackages, airports.csv data bundle,
systemd unit files, and full test scaffold. All three quality gates
pass: pytest 12/12, ruff check zero violations, ruff format clean.

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

tests/conftest.py

@@ -0,0 +1,8 @@
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def tmp_config_path(tmp_path: Path) -> Path:
+    return tmp_path / "config.json"