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

database/migrations/2026_04_28_151408_add_connection_timeout_to_server_settings.php

@@ -0,0 +1,22 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('server_settings', function (Blueprint $table) {
+            $table->integer('connection_timeout')->default(10)->after('deployment_queue_limit');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('server_settings', function (Blueprint $table) {
+            $table->dropColumn('connection_timeout');
+        });
+    }
+};