Rename package to project-manager

- composer.json: aneurin/php-todo-list -> aneurin/php-project-manager
- web/package.json (+ lockfile): "web" -> "project-manager-web"
- docker-compose.yml image tags: php-todo-list -> php-project-manager,
  php-todo-web -> php-project-manager-web

The directory, the Compose project prefix (derived from the directory name),
and the git remote still carry the old name and are left as-is.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

composer.json

@@ -1,5 +1,5 @@
 {
-    "name": "aneurin/php-todo-list",
+    "name": "aneurin/php-project-manager",
     "description": "Simple project-management REST API + SPA (PHP, SQLite)",
     "type": "project",
     "license": "MIT",