Initial commit: EventTracker desktop app + Android companion

Desktop: GTK3 + matplotlib app tracking arbitrary events (button ->
timestamp -> CSV), with per-event stats, trend charts, settings
(rename/add events, relocate data file), and a reset-with-backup flow.
Portable desktop launcher via a .desktop.in template + install script,
no machine-specific paths baked in.

Android: minimal Kivy v1 companion reading/writing the same CSV format,
plus buildozer build tooling isolated in a venv and a local p4a recipe
override for kivy (see CLAUDE.md for why).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

android/setup-build-env.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# Creates an isolated venv for buildozer/cython so the Android build
+# tooling never touches Arch's externally-managed system Python.
+# Safe to re-run — skips venv creation if it already exists, and
+# pip install is idempotent.
+set -euo pipefail
+
+# ---- Configuration ----
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+BUILD_DIR="$SCRIPT_DIR/build"
+VENV_DIR="$BUILD_DIR/venv"
+
+mkdir -p "$BUILD_DIR"
+
+if [ ! -d "$VENV_DIR" ]; then
+    echo "Creating venv at $VENV_DIR"
+    # Plain isolated venv — no --system-site-packages. buildozer's own
+    # `pip install --user ...` bootstrap step (for p4a's build deps) is
+    # skipped automatically when it sees $VIRTUAL_ENV set, which build.sh
+    # sets — see the comment there. --system-site-packages was tried
+    # briefly to work around that instead, but it leaks the real system
+    # Python's installed packages into what buildozer decides the app
+    # needs to bundle, which is worse.
+    python3 -m venv "$VENV_DIR"
+fi
+
+"$VENV_DIR/bin/pip" install --upgrade pip
+"$VENV_DIR/bin/pip" install buildozer cython
+
+echo
+echo "Build environment ready."
+echo "Run the build with: $SCRIPT_DIR/build.sh android debug"
+echo "(or activate it directly: source $VENV_DIR/bin/activate)"