Add initial backend, CLI, and frontend scaffold

Bootstrap repository with multi-component scaffolding: a Spring Boot backend (Maven wrapper, pom.xml, BackendApplication, test, resources, .gitignore/.gitattributes), a Go CLI app using Cobra (root + subcommands: diff, log, login, pull, push, set, unset), prebuilt CLI binaries and a build script, and a Next.js frontend (configs, package.json, styles, pages, and static assets). This commit provides the skeleton for development across backend, CLI, and frontend components.

backend/pom.xml

@@ -0,0 +1,128 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>4.0.3</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>com.envsync</groupId>
+	<artifactId>backend</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>backend</name>
+	<description>Backend for EnvSync</description>
+	<url/>
+	<licenses>
+		<license/>
+	</licenses>
+	<developers>
+		<developer/>
+	</developers>
+	<scm>
+		<connection/>
+		<developerConnection/>
+		<tag/>
+		<url/>
+	</scm>
+	<properties>
+		<java.version>21</java.version>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-actuator</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-redis</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security-oauth2-client</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security-oauth2-resource-server</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-validation</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-webmvc</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-devtools</artifactId>
+			<scope>runtime</scope>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.postgresql</groupId>
+			<artifactId>postgresql</artifactId>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-actuator-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-redis-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security-oauth2-client-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security-oauth2-resource-server-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-security-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-validation-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-webmvc-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>