feat(cli): implement config management CLI commands (Phase 4)

Add comprehensive config management commands with 7 subcommands for
viewing, editing, validating, backing up, and migrating configurations.

New Commands:
- envg config get <key>: Get config value with dot notation support
  * Examples: envg config get package.name, envg config get environments.default
  * Returns formatted JSON for objects, plain values for primitives

- envg config set <key> <value>: Set config value with dot notation
  * Auto-migrates v1→v2 before setting values
  * Updates metadata timestamps automatically
  * Type-safe value conversion (boolean, number, array, string)

- envg config list: Display complete configuration as JSON
  * Works with both v1 and v2 configs
  * Pretty-printed output

- envg config validate: Validate current configuration
  * Checks all required fields
  * Validates environment consistency (default must be in allowed list)
  * Provides detailed error messages for v2 configs

- envg config backup: Create timestamped backup
  * Default path: .envguard/config.backup.{timestamp}.json
  * Custom path via --output flag

- envg config restore <file>: Restore from backup
  * Auto-creates backup of current config before restoring
  * Validates backup file format
  * Supports both v1 and v2 backups

- envg config migrate: Migrate v1→v2 manually
  * Auto-detects current version
  * Creates backup before migration
  * Skips if already v2

Implementation Details:
- packages/cli/src/commands/config.action.ts: Core implementation (430 lines)
  * configGetAction: Nested object access with dot notation
  * configSetAction: Type-aware value setting with auto-migration
  * configListAction: Pretty JSON display
  * configValidateAction: Comprehensive validation with detailed errors
  * configBackupAction: Timestamped backup creation
  * configRestoreAction: Safe restore with auto-backup
  * configMigrateAction: v1→v2 migration workflow
  * Helper functions: getNestedValue(), setNestedValue()

- packages/cli/src/cli.ts: Command registration
  * Registered config command with 7 subcommands
  * Commander.js subcommand pattern
  * Consistent --verbose flag support

- packages/cli/src/commands/index.ts: Export config actions

Features:
- Dot notation for nested config access (e.g., "package.name", "environments.allowed")
- Auto-migration from v1→v2 when setting values
- Metadata tracking (lastModified, modifiedBy)
- Safe restore with automatic backup creation
- Type-safe value conversion (string→boolean/number/array)
- Comprehensive validation with actionable error messages
- Timestamped backups for audit trails

CLI Help Output:
$ envg config --help
Usage: envg config [options] [command]

Manage EnvGuard configuration

Commands:
  get [options] <key>          Get a config value (supports dot notation)
  set [options] <key> <value>  Set a config value (supports dot notation)
  list [options]               List all config values
  validate [options]           Validate current config
  backup [options]             Backup current config
  restore [options] <file>     Restore config from backup
  migrate [options]            Migrate config from v1 to v2

All Tests Passing:
- @envguard/core: 58 tests
- @envguard/node: 88 tests
- @envguard/cli: 12 tests
- Build: Clean for all packages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: amannirala13

packages/cli/src/cli.ts

@@ -3,6 +3,13 @@
 import { program } from 'commander';
 import {
   checkAction,
+  configBackupAction,
+  configGetAction,
+  configListAction,
+  configMigrateAction,
+  configRestoreAction,
+  configSetAction,
+  configValidateAction,
   copyAction,
   delAction,
   editAction,
@@ -242,6 +249,69 @@ program
     }
   );
 
+// Config command with subcommands
+const configCommand = program
+  .command('config')
+  .description('Manage EnvGuard configuration');
+
+configCommand
+  .command('get <key>')
+  .description('Get a config value (supports dot notation)')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (key: string, options) => {
+    await configGetAction(key, options);
+  });
+
+configCommand
+  .command('set <key> <value>')
+  .description('Set a config value (supports dot notation)')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (key: string, value: string, options) => {
+    await configSetAction(key, value, options);
+  });
+
+configCommand
+  .command('list')
+  .description('List all config values')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (options) => {
+    await configListAction(options);
+  });
+
+configCommand
+  .command('validate')
+  .description('Validate current config')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (options) => {
+    await configValidateAction(options);
+  });
+
+configCommand
+  .command('backup')
+  .description('Backup current config')
+  .option('-o, --output <path>', 'Output path for backup file')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (options) => {
+    await configBackupAction(options);
+  });
+
+configCommand
+  .command('restore <file>')
+  .description('Restore config from backup')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (file: string, options) => {
+    await configRestoreAction(file, options);
+  });
+
+configCommand
+  .command('migrate')
+  .description('Migrate config from v1 to v2')
+  .option('--no-backup', 'Skip creating backup before migration')
+  .option('-v, --verbose', 'Enable verbose logging', false)
+  .action(async (options) => {
+    await configMigrateAction(options);
+  });
+
 program
   .command('status')
   .description('Show current EnvGuard status and configuration')