fix: implement 22 security pentest remediation fixes

Server-side session management with SHA-256 hashed tokens and HttpOnly
cookies. Auth middleware gating all RPC/WS/proxy routes with method
allowlist. Login rate limiting (5/60s per IP). CORS restricted to
config origin. Docker registry allowlist. App ID and path validation.
P2P message sanitization (HTML + log injection). Onion address and
known-peer validation. Nginx security headers (CSP, X-Frame-Options,
etc.) and AIUI proxy auth. Systemd hardening (non-root, NoNewPrivileges,
ProtectSystem).

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

core/archipelago/src/api/rpc/container.rs

@@ -17,6 +17,22 @@ impl RpcHandler {
             .and_then(|v| v.as_str())
             .ok_or_else(|| anyhow::anyhow!("Missing manifest_path"))?;
 
+        // Validate manifest path: reject path traversal and paths outside apps/
+        if manifest_path.contains("..") {
+            return Err(anyhow::anyhow!(
+                "Invalid manifest_path: path traversal not allowed"
+            ));
+        }
+        let path = std::path::Path::new(manifest_path);
+        if path.is_absolute() {
+            let apps_dir = self.config.data_dir.join("apps");
+            if !path.starts_with(&apps_dir) {
+                return Err(anyhow::anyhow!(
+                    "Invalid manifest_path: must be under the apps directory"
+                ));
+            }
+        }
+
         // Load manifest
         let manifest_content = tokio::fs::read_to_string(manifest_path)
             .await