Add macOS host support

Cherry-picks the macOS-specific pieces from PR #5: Python daemon using
bleak (CoreBluetooth backend), LaunchAgent template, flash-mac.sh, and
install-mac.sh. Token is read from the macOS Keychain ("Claude
Code-credentials" service); Linux behavior is unchanged. README split
into "macOS installation" and "Linux installation" sections with
parallel Flash / Pair / Install subsections.

Co-Authored-By: Chris Davidson <36679917+lorddavidson@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitignore

@@ -11,3 +11,10 @@ firmware/.vscode/
 # Node tooling deps (npm install --no-save)
 tools/node_modules/
 tools/package-lock.json
+
+# Mac daemon venv
+daemon/.venv/
+
+# Python bytecode cache
+__pycache__/
+*.pyc