feat(server): add configurable SSH connection timeout per server

Add `connection_timeout` field to server settings, allowing per-server
override of the global SSH connection timeout constant.

- Migration adds `connection_timeout` integer column (default 10s)
- `ServerSetting` model exposes and casts the new field
- `SshMultiplexingHelper::getConnectionTimeout()` resolves per-server
  value with fallback to `constants.ssh.connection_timeout`
- All SSH/SCP command builders use the new resolver instead of the
  global config directly
- Livewire `Show` component binds `connectionTimeout` with validation
  (1–300 seconds) and syncs to/from the model
- UI input added to server settings form with helper text
- Feature tests cover default, persistence, resolver, and fallback

app/Models/ServerSetting.php

@@ -49,6 +49,7 @@ use OpenApi\Attributes as OA;
         'updated_at' => ['type' => 'string'],
         'delete_unused_volumes' => ['type' => 'boolean', 'description' => 'The flag to indicate if the unused volumes should be deleted.'],
         'delete_unused_networks' => ['type' => 'boolean', 'description' => 'The flag to indicate if the unused networks should be deleted.'],
+        'connection_timeout' => ['type' => 'integer', 'description' => 'SSH connection timeout in seconds.'],
     ]
 )]
 class ServerSetting extends Model
@@ -97,6 +98,7 @@ class ServerSetting extends Model
         'is_terminal_enabled',
         'deployment_queue_limit',
         'disable_application_image_retention',
+        'connection_timeout',
     ];
 
     protected $casts = [
@@ -108,6 +110,7 @@ class ServerSetting extends Model
         'is_usable' => 'boolean',
         'is_terminal_enabled' => 'boolean',
         'disable_application_image_retention' => 'boolean',
+        'connection_timeout' => 'integer',
     ];
 
     protected static function booted()