refactor(models): extract defaultStandaloneDockerAttributes method on Server

Extract duplicated inline StandaloneDocker attribute arrays in the
Server boot lifecycle into a dedicated method, eliminating repetition
between the root-server (id=0) and normal-server paths.

Also harden the shared_environment_variables migration by wrapping
DDL statements in DB::transaction() and using DROP CONSTRAINT IF EXISTS
to make the migration safely re-runnable.

Add unit test covering the extracted method to verify uuid is always
present in bootstrap attributes.

database/migrations/2025_12_24_095507_add_server_to_shared_environment_variables_table.php

@@ -5,17 +5,23 @@ use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Schema;
 
-return new class extends Migration {
+return new class extends Migration
+{
     /**
      * Run the migrations.
      */
     public function up(): void
     {
-        DB::statement("ALTER TABLE shared_environment_variables DROP CONSTRAINT shared_environment_variables_type_check");
-        DB::statement("ALTER TABLE shared_environment_variables ADD CONSTRAINT shared_environment_variables_type_check CHECK (type IN ('team', 'project', 'environment', 'server'))");
-        Schema::table('shared_environment_variables', function (Blueprint $table) {
-            $table->foreignId('server_id')->nullable()->constrained()->onDelete('cascade');
-            $table->unique(['key', 'server_id', 'team_id']);
+        DB::transaction(function () {
+            DB::statement('ALTER TABLE shared_environment_variables DROP CONSTRAINT IF EXISTS shared_environment_variables_type_check');
+            DB::statement("ALTER TABLE shared_environment_variables ADD CONSTRAINT shared_environment_variables_type_check CHECK (type IN ('team', 'project', 'environment', 'server'))");
+            Schema::table('shared_environment_variables', function (Blueprint $table) {
+                $table->foreignId('server_id')->nullable()->constrained()->onDelete('cascade');
+                // NULL != NULL in PostgreSQL unique indexes, so this only enforces uniqueness
+                // for server-scoped rows (where server_id is non-null). Other scopes are covered
+                // by existing unique constraints on ['key', 'project_id', 'team_id'] and ['key', 'environment_id', 'team_id'].
+                $table->unique(['key', 'server_id', 'team_id']);
+            });
         });
     }
 
@@ -24,12 +30,14 @@ return new class extends Migration {
      */
     public function down(): void
     {
-        Schema::table('shared_environment_variables', function (Blueprint $table) {
-            $table->dropUnique(['key', 'server_id', 'team_id']);
-            $table->dropForeign(['server_id']);
-            $table->dropColumn('server_id');
+        DB::transaction(function () {
+            Schema::table('shared_environment_variables', function (Blueprint $table) {
+                $table->dropUnique(['key', 'server_id', 'team_id']);
+                $table->dropForeign(['server_id']);
+                $table->dropColumn('server_id');
+            });
+            DB::statement('ALTER TABLE shared_environment_variables DROP CONSTRAINT IF EXISTS shared_environment_variables_type_check');
+            DB::statement("ALTER TABLE shared_environment_variables ADD CONSTRAINT shared_environment_variables_type_check CHECK (type IN ('team', 'project', 'environment'))");
         });
-        DB::statement("ALTER TABLE shared_environment_variables DROP CONSTRAINT shared_environment_variables_type_check");
-        DB::statement("ALTER TABLE shared_environment_variables ADD CONSTRAINT shared_environment_variables_type_check CHECK (type IN ('team', 'project', 'environment'))");
     }
 };