feat: configurable stop grace period for applications

Adds stop_grace_period to application settings (seconds, 1-3600, default 30).
Used in place of the hardcoded docker stop -t 30 in the four places that
stop application containers: rolling update shutdown, manual stop, stop on
another server, and preview deployment stop.

Non-positive values fall back to the default via ($val > 0) ? $val : default,
with tests covering 0 and -10 so the cast does not blow up if a bad value
ever lands in the db.

Picks up Jack Coy's work from #7125 which went dormant. His commits are
squashed here with credit below.

Co-authored-by: Jack Coy <jackman3000@gmail.com>

database/migrations/2025_11_05_091558_add_stop_grace_period_to_application_settings.php

@@ -0,0 +1,31 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('application_settings', function (Blueprint $table) {
+            $table->integer('stop_grace_period')
+                ->nullable()
+                ->after('use_build_secrets')
+                ->comment('Seconds to wait for graceful shutdown before forcing container stop (1-3600). Null uses default of 30 seconds.');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('application_settings', function (Blueprint $table) {
+            $table->dropColumn('stop_grace_period');
+        });
+    }
+};