build: M1 Dockerized development stack with PHP skeleton, config/logging, Tailwind assets, and wrappers

Implements MeshVault M1 (issues #6–11):

- Four-service Docker Compose stack (nginx, PHP-FPM 8.3, PostgreSQL 17, Node assets)
- Slim 4 + PHP-DI routing with escaped PHP views and production/dev error handling
- Immutable validated AppConfig with redacted diagnostics
- JSON stdout Monolog logging with job-scoped context
- Tailwind CSS v4 deterministic locked builds with template scanning
- POSIX and PowerShell dev wrappers (up/down/test/lint/assets/watch)
- Startup config validation fails before FPM serves as unprivileged www-data
- migrate/seed explicitly unavailable until M2 (#12); #10 remains open

Verified via clean-start acceptance on remote host (keith@192.168.2.23).

bin/check-config.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+$stage = 'autoload';
+try {
+    require dirname(__DIR__) . '/vendor/autoload.php';
+    $stage = 'configuration';
+    \MeshVault\Config\AppConfig::fromEnvironment(getenv());
+    fwrite(STDOUT, "Configuration valid for runtime user.\n");
+} catch (\Throwable $exception) {
+    $detail = $stage === 'configuration' && $exception instanceof \InvalidArgumentException
+        ? $exception->getMessage() : 'Install dependencies and check bootstrap files.';
+    fwrite(STDERR, 'Configuration check failed: ' . $detail . "\n");
+    exit(1);
+}