Previously, 'Erneut versuchen' and 'Ausgewählte starten' did nothing
when a batch was already running (uploading=true). Failed jobs were
set to 'Wartet' but never actually uploaded because they couldn't be
added to the running batch.
New: upload-manager.addJobs() allows adding tasks to a running batch.
When a batch is active and user retries/starts jobs, they're injected
into the running batch via IPC 'add-jobs-to-batch'. The upload manager
starts processing them immediately using the existing semaphores.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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