v0.2.0: Fix List Jobs bug, TLS 1.3 enforcement, client_disconnect_timeout, RwLock contention

Bug fixes:
- Fix List Jobs connection reset: Add client_disconnect_timeout (5s) to prevent TLS write truncation
- Enforce TLS 1.3 only: Add with_protocol_versions(&[&TLS13]) to rustls ServerConfig
- Fix RwLock contention: Release read lock before sorting in list_jobs()
- Fix systemd service: Remove ProtectSystem=strict (blocks package management)
- Fix systemd service: Change Type=notify to Type=simple (fixes restart hangs)
- Fix systemd service: Add DEBIAN_FRONTEND=noninteractive
- Fix systemd service: Add ReadWritePaths for apt/dpkg paths

CI/CD:
- Add Ubuntu 22.04 build job to CI workflow

E2E Testing:
- Add comprehensive E2E test suite (test_e2e.py)
- Tests cover health, packages, patches, jobs, security, and reboot endpoints

Other:
- Bump version to 0.2.0
- Add lessons learned documentation

src/main.rs

@@ -141,6 +141,8 @@ async fn main() -> Result<()> {
     .workers(4)
     // VULN-004: Configure header size limit to 8KB to prevent DoS via oversized headers
     .client_request_timeout(std::time::Duration::from_secs(5))
+    // FIX: Set explicit client disconnect timeout to prevent connection resets on larger responses
+    .client_disconnect_timeout(std::time::Duration::from_secs(5))
     .keep_alive(std::time::Duration::from_secs(15))
     .max_connection_rate(1000);
     info!(