feat: Add --host parameter support to login command

Added --host/-h option to the login command to support authentication
against self-hosted Fleetbase instances.

Features:
- Accepts full URL with protocol (http:// or https://)
- Auto-adds https:// if protocol is missing
- Constructs registry URL from host automatically
- Falls back to https://api.fleetbase.io if not specified

Usage:
  flb login -u username -p password -e email@example.com
  flb login -u username -p password -e email@example.com --host http://localhost:8000
  flb login -u username -p password -e email@example.com --host myinstance.com

This completes the self-hosted authentication flow:
1. flb register --host <host>
2. flb verify -e <email> -c <code> --host <host>
3. flb login -u <username> -p <password> -e <email> --host <host>

Author: Manus AI

index.js

@@ -1204,7 +1204,15 @@ function loginCommand (options) {
     const username = options.username;
     const password = options.password;
     const email = options.email;
-    const registry = options.registry || defaultRegistry;
+    const host = options.host || 'https://api.fleetbase.io';
+    
+    // Ensure host has protocol
+    const apiHost = host.startsWith('http://') || host.startsWith('https://') 
+        ? host 
+        : `https://${host}`;
+    
+    // Construct registry URL from host
+    const registry = options.registry || `${apiHost}/registry/v1`;
     const scope = options.scope || '';
     const quotes = options.quotes || '';
     const configPath = options.configPath || '';
@@ -1391,6 +1399,7 @@ program
     .option('-u, --username <username>', 'Username for the registry')
     .option('-p, --password <password>', 'Password for the registry')
     .option('-e, --email <email>', 'Email associated with your account')
+    .option('-h, --host <host>', 'API host with protocol (default: https://api.fleetbase.io)')
     .option('-r, --registry <registry>', 'Registry URL', defaultRegistry)
     .option('--scope <scope>', 'Scope for the registry')
     .option('--quotes <quotes>', 'Quotes option for npm-cli-login')