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>

app/build.gradle.kts

@@ -0,0 +1,78 @@
+plugins {
+    alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.android)
+    alias(libs.plugins.kotlin.compose)
+    alias(libs.plugins.ksp)
+}
+
+android {
+    namespace = "net.metacircular.engpad"
+    compileSdk = 36
+
+    defaultConfig {
+        applicationId = "net.metacircular.engpad"
+        minSdk = 30
+        targetSdk = 36
+        versionCode = 1
+        versionName = "0.1.0"
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = true
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    buildFeatures {
+        compose = true
+    }
+
+    lint {
+        warningsAsErrors = true
+        abortOnError = true
+        checkDependencies = true
+        // AGP 9.x requires Gradle 9.x; suppress until we're ready to migrate
+        disable += "AndroidGradlePluginVersion"
+    }
+}
+
+kotlin {
+    jvmToolchain(17)
+}
+
+dependencies {
+    implementation(libs.androidx.core.ktx)
+    implementation(libs.androidx.activity.compose)
+
+    implementation(platform(libs.compose.bom))
+    implementation(libs.compose.ui)
+    implementation(libs.compose.ui.tooling.preview)
+    implementation(libs.compose.material3)
+    debugImplementation(libs.compose.ui.tooling)
+
+    implementation(libs.navigation.compose)
+
+    implementation(libs.lifecycle.viewmodel.compose)
+    implementation(libs.lifecycle.runtime.compose)
+
+    implementation(libs.room.runtime)
+    implementation(libs.room.ktx)
+    ksp(libs.room.compiler)
+
+    implementation(libs.coroutines.android)
+
+    testImplementation(libs.junit)
+    testImplementation(libs.coroutines.test)
+    testImplementation(libs.room.testing)
+}