Add missing app files and fix Docker configuration

- Add all PHP app files (controllers, middleware, providers, models, enums)
  that were previously gitignored via app/.gitignore wildcard
- Fix app/.gitignore to no longer ignore all files
- Fix docker-compose.yml: use named volume for postgres to avoid chown permission errors on server
- Fix Dockerfile: use --classmap-authoritative for composer dump-autoload

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Http/Middleware/PreventRequestsDuringMaintenance.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Illuminate\Foundation\Http\Middleware\PreventRequestsDuringMaintenance as Middleware;
+
+class PreventRequestsDuringMaintenance extends Middleware
+{
+    protected $except = [
+        //
+    ];
+}