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>

src/planemapper/display.py

@@ -0,0 +1,12 @@
+from typing import Protocol
+
+from PIL import Image
+
+
+class DisplayInterface(Protocol):
+    def show(self, image: Image.Image) -> None: ...
+
+
+class NullDisplay:
+    def show(self, image: Image.Image) -> None:
+        pass