feat: implement remote tls/ssh security, isolate system stats, and polish ux

- NodeRegistry: wire TLS ca/cert/key into Dockerode when present on node config
- index.ts: /api/system/stats now branches on node type — remote nodes use docker.info() for CPU/RAM, local keeps systeminformation; disk gracefully returns null for remote
- index.ts: POST /api/nodes now persists tls_ca, tls_cert, tls_key fields
- FileSystemService: throw clean error on missing/empty compose_dir instead of crashing path.join
- FileSystemService: guard getStacks() against falsy item.name entries
- SSHFileAdapter: filter undefined/non-string names from SFTP readdir before returning
- NodeManager: add SSH Authentication Type toggle (Password vs Private Key)
- NodeManager: add Enable TLS toggle with conditional CA/cert/key textarea fields
- NodeManager: auto-test connection immediately after node creation
- NodeManager: replace "Strategy B" copy with Docker TCP setup instructions
- NodeManager: add pr-8 to header and DialogHeader to prevent overlap with parent dialog X button

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

backend/src/services/FileSystemService.ts

@@ -11,14 +11,17 @@ export class FileSystemService {
 
   constructor(nodeId?: number) {
     this.nodeId = nodeId ?? NodeRegistry.getInstance().getDefaultNodeId();
-    
+
     const node = NodeRegistry.getInstance().getNode(this.nodeId);
 
     if (!node || node.type === 'local' || !node.host) {
       this.baseDir = process.env.COMPOSE_DIR || '/app/compose';
       this.adapter = new LocalFileAdapter();
     } else {
-      this.baseDir = node.compose_dir || '/app/compose';
+      this.baseDir = node.compose_dir;
+      if (!this.baseDir || typeof this.baseDir !== 'string' || this.baseDir.trim() === '') {
+        throw new Error(`Remote node "${node.name}" has no compose_dir configured. Please set a compose directory in the Node Manager.`);
+      }
       this.adapter = new SSHFileAdapter(node);
     }
   }
@@ -77,6 +80,7 @@ export class FileSystemService {
 
       for (const item of items) {
         if (!item.isDirectory()) continue;
+        if (!item.name || typeof item.name !== 'string') continue;
 
         const stackDir = path.join(this.baseDir, item.name);
         const hasCompose = await this.hasComposeFile(stackDir);