Add backend API for projects & snapshots

Introduce full backend API surface for projects, snapshots and user pubkeys: controllers, DTOs, JPA entities, repositories, services, and tests. Add SecurityConfig improvements (JWT decoder, audience/issuer/timestamp validation and CORS), a GlobalExceptionHandler for consistent error responses, and remove a stray test call from BackendApplication. Also update README (architecture, docs, CLI/Frontend/Backend notes), add CLAUDE.md, VSCode settings, and multiple frontend/CLI Rust changes. Small housekeeping: add .DS_Store and test adjustments.

cli/envsync-cli/src/commands/logout.rs

@@ -0,0 +1,26 @@
+use anyhow::Result;
+
+use crate::config::Config;
+
+pub fn run() -> Result<()> {
+    let mut config = Config::load()?;
+
+    if config.auth.is_none() {
+        println!("Not currently logged in.");
+        return Ok(());
+    }
+
+    let email = config
+        .auth
+        .as_ref()
+        .map(|a| a.user_email.as_str())
+        .unwrap_or("unknown")
+        .to_string();
+
+    config.auth = None;
+    // Keep the keypair — user can re-authenticate without re-generating keys.
+    config.save()?;
+
+    println!("Logged out ({email}).");
+    Ok(())
+}