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).

templates/error.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+?>
+<!doctype html>
+<html lang="en">
+<head><meta charset="utf-8"><title><?= $escape($data['title']) ?></title></head>
+<body><h1><?= $escape($data['title']) ?></h1><pre><?= $escape($data['detail']) ?></pre></body>
+</html>

templates/home.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+?>
+<!doctype html>
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title><?= $escape($data['title']) ?></title>
+    <link rel="stylesheet" href="/build/app.css">
+</head>
+<body><h1 class="text-blue-600"><?= $escape($data['title']) ?></h1><p>Your managed 3D model library.</p></body>
+</html>