Implement Phase 1: project skeleton and data layer

Android project with Kotlin, Jetpack Compose, and Room. Includes:
- Gradle build system with version catalog, foojay JDK resolver, lint config
- Room entities (Notebook, Page, Stroke) with packed float BLOB encoding
- DAOs and repositories for all entities
- Unit tests for blob roundtrip and PageSize enum (10 tests, all passing)
- Minimal Application class and stub MainActivity

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea
+/build
+/app/build
+/captures
+.externalNativeBuild
+.cxx
+*.apk
+*.ap_
+*.aab
+/srv/