Revert timeout workarounds from #725, keep chunk length increases

[mishig25]

Summary

• Reverts the processing logic changes from commit 894c424 (Fix GitHub Action timeout during Meili indexation #725) that added 1-hour delays between libraries and removed @wait_for_task_completion decorator
• Restores the original batch processing approach where all embeddings are generated and uploaded together
• Keeps the chunk length increases (2000→4000 for CHUNK_LEN_CHARS, 1000→2000 for excerpt-length) which help reduce total embedding count

Test plan

• Verify the embeddings workflow runs successfully without the 1-hour delays
• Confirm the @wait_for_task_completion decorator properly waits for Meilisearch tasks