fix(server): remove redundant SSH work from server checks

- ServerCheckJob uses the stored reachability state instead of a second SSH
  probe. One failed probe no longer marks the server unreachable without
  UNREACHABLE_THRESHOLD or marks all its resources exited.
- Do not dispatch ServerCheckJob for build servers and Swarm workers.
- Check cloud provider state every 5 minutes instead of every minute.
- ServerPatchCheckJob uses isFunctional() and drops the unused retries.
- Delete the unused ServerCleanupMux job.
- Disable SSH multiplexing per command. The global config change stayed in
  the queue worker, so later jobs (also deployments) ran without mux.

app/Jobs/ServerConnectionCheckJob.php

@@ -5,7 +5,6 @@ namespace App\Jobs;
 use App\Events\ServerReachabilityChanged;
 use App\Helpers\SshMultiplexingHelper;
 use App\Models\Server;
-use App\Services\ConfigurationRepository;
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldBeEncrypted;
 use Illuminate\Contracts\Queue\ShouldQueue;
@@ -55,12 +54,6 @@ class ServerConnectionCheckJob implements ShouldBeEncrypted, ShouldQueue
         return [(new WithoutOverlapping('server-connection-check-'.$this->server->uuid))->expireAfter($this->timeout + 30)->dontRelease()];
     }
 
-    private function disableSshMux(): void
-    {
-        $configRepository = app(ConfigurationRepository::class);
-        $configRepository->disableSshMux();
-    }
-
     public function handle(): void
     {
         if ($this->server->hasPlaceholderIp()) {
@@ -87,11 +80,6 @@ class ServerConnectionCheckJob implements ShouldBeEncrypted, ShouldQueue
                 return;
             }
 
-            // Temporarily disable mux if requested
-            if ($this->disableMux) {
-                $this->disableSshMux();
-            }
-
             // Check basic connectivity first
             $isReachable = $this->checkConnection();
 
@@ -291,7 +279,7 @@ class ServerConnectionCheckJob implements ShouldBeEncrypted, ShouldQueue
     private function runDockerCommand(string $command): ?string
     {
         try {
-            $process = Process::timeout(self::DOCKER_TIMEOUT_SECONDS)->run($this->sshCommand($command));
+            $process = Process::timeout(self::DOCKER_TIMEOUT_SECONDS)->run($this->sshCommand($command, disableMultiplexing: $this->disableMux));
         } catch (\Throwable $e) {
             Log::debug('ServerConnectionCheck: Docker command failed', [
                 'server_id' => $this->server->id,