initial: Kotlin/Gradle skeleton for cloud-installer

Compiles to a 3.4 MB fat jar via shadow plugin.
Entrypoint with CLI dispatch (pull/push subcommands) + FlatLaf init.
Real sync logic stubbed; lands in subsequent commits per task plan.

Build via containerized gradle (8.10.2 + jdk21) to sidestep the
Kotlin 2.1 + JDK 26 compiler crash. Documented in README.

CI workflow tags-only release artifact upload prepared (needs
RELEASE_TOKEN secret in repo settings before first tag).

.gitignore

@@ -0,0 +1,8 @@
+.gradle/
+build/
+out/
+*.iml
+.idea/
+.vscode/
+*.swp
+local.properties