justfile: standardise test recipes to lint-php/lint-css/lint-js/test + add fix recipe

- Removed ambiguous aliases: phpstan, cs-check (both pointed to lint-php which
  also ran php-cs-fixer, making the names misleading)
- Removed syntax (php -l) — redundant, phpstan already catches parse errors
- Split lint-biome into lint-css and lint-js with correct paths
- Added lint meta-recipe that runs all three linters
- Added fix recipe: biome check --write (CSS/JS format+lint) + php-cs-fixer fix (PHP)
- Updated build-lint to delegate to lint-css + lint-js

app/src/icon.php

@@ -10,7 +10,8 @@
  * Usage: <?= icon('trash') ?>
  *        <?= icon('search', 0, 'header-search-icon') ?>
  */
-function icon(string $name, int $size = 0, string $class = ''): string {
+function icon(string $name, int $size = 0, string $class = ''): string
+{
     $path = APP_ROOT . "/public/assets/icons/{$name}.svg";
     if (!file_exists($path)) {
         return "<!-- icon not found: {$name} -->";