feat(samples): scaffold Kotlin backend Gradle project

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pengying

samples/kotlin/.env.example

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+# Grid API Credentials (from https://app.lightspark.com)
+GRID_API_TOKEN_ID=your_api_token_id
+GRID_API_CLIENT_SECRET=your_api_client_secret
+
+# Webhook verification (P-256 public key, PEM format)
+GRID_WEBHOOK_PUBLIC_KEY=your_webhook_public_key

samples/kotlin/build.gradle.kts

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+plugins {
+    kotlin("jvm") version "2.1.21"
+    kotlin("plugin.serialization") version "2.1.21"
+    id("io.ktor.plugin") version "3.1.3"
+}
+
+kotlin {
+    jvmToolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+}
+
+group = "com.grid.sample"
+version = "0.0.1"
+
+application {
+    mainClass = "io.ktor.server.netty.EngineMain"
+    applicationDefaultJvmArgs = listOf("-Dio.ktor.development=true")
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    // Ktor server
+    implementation("io.ktor:ktor-server-core:3.1.3")
+    implementation("io.ktor:ktor-server-netty:3.1.3")
+    implementation("io.ktor:ktor-server-cors:3.1.3")
+    implementation("io.ktor:ktor-server-sse:3.1.3")
+    implementation("io.ktor:ktor-server-content-negotiation:3.1.3")
+    implementation("io.ktor:ktor-server-config-yaml:3.1.3")
+
+    // Grid Kotlin SDK
+    implementation("com.lightspark.grid:lightspark-grid-kotlin:0.4.0")
+
+    // JSON
+    implementation("com.fasterxml.jackson.module:jackson-module-kotlin:2.18.2")
+
+    // Environment
+    implementation("io.github.cdimascio:dotenv-kotlin:6.4.1")
+
+    // Logging
+    implementation("ch.qos.logback:logback-classic:1.5.6")
+}

samples/kotlin/gradle.properties

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+kotlin.code.style=official
+org.gradle.jvmargs=-Xmx1024m

samples/kotlin/gradle/wrapper/gradle-wrapper.jar

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists