Fix app name generation: lowercase only, skip deleted records

CapRover only allows lowercase letters and single hyphens. The generator
now strips invalid chars, forces lowercase suffix, and ignores deleted
instances when checking for collisions.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Services/InstanceProvisionerService.php

@@ -220,13 +220,18 @@ public function updateEnvVars(Instance $instance, array $vars): void
 
     private function generateAppName(string $academyName): string
     {
+        // CapRover only allows lowercase letters and single hyphens
         $base = Str::slug($academyName);
+        $base = preg_replace('/[^a-z0-9\-]/', '', $base);
+        $base = trim(preg_replace('/-+/', '-', $base), '-');
         $base = Str::limit($base, 30, '');
 
-        if (!Instance::where('app_name', $base)->exists()) {
+        if (!Instance::where('app_name', $base)->whereNot('status', 'deleted')->exists()) {
             return $base;
         }
 
-        return $base . '-' . Str::random(4);
+        // Suffix must also be lowercase only
+        $suffix = strtolower(Str::random(4));
+        return Str::limit($base, 25, '') . '-' . $suffix;
     }
 }