chore: add repo meta files (LICENSE, README, CHANGELOG, gitignore)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

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+# Calendula
+
+A modern Material 3 Expressive calendar app for Android.
+
+Calendula is named after the flower of the same name, whose name comes from
+the Latin *kalendae* — the first day of the month — the same root as the
+word "calendar". Calendula reads from Android's built-in `CalendarContract`,
+so any calendar source synced to your device (CalDAV via DAVx5, Google,
+local, WebCal subscriptions, ...) is shown.
+
+## Features (V1)
+
+- Month, Week, and Day views
+- Read-only event details (write support comes in V2)
+- Multi-calendar visibility toggle
+- Material You Dynamic Color (Android 12+)
+- Light/Dark theme follows system
+- German + English UI
+
+## Building
+
+Requires Android SDK 36 and JDK 17. The Gradle wrapper is checked in, so no host Gradle install is needed:
+
+```bash
+# Build debug APK
+./gradlew assembleDebug
+
+# Run unit tests
+./gradlew test
+
+# Run lint
+./gradlew lint
+```
+
+If your default JDK is something other than 17, set `JAVA_HOME` explicitly:
+
+```bash
+JAVA_HOME=/path/to/jdk-17 ./gradlew assembleDebug
+```
+
+## License
+
+[MIT](LICENSE) — Jean-Luc Makiola, 2026