fix: sync to x replace fuser with mtime check

[citruscosmos]

Description

This PR replaces the fuser command with an mtime (modification time) check in the sync-to-x data synchronization process.

Previously, using fuser caused significant slowdowns when operating over network file systems (NFS). Using an mtime-based check provides a much more efficient way to determine if a file is still actively being written to.

Additionally, this PR includes the following updates:

• Configurable Active-File Threshold: The threshold for determining an active file based on mtime is now configurable via an Ansible parameter.
• Transfer Bandwidth Limitation Fix: Adjusted the rsync bandwidth limit (increased from 100m to 200m) to resolve transfer bottlenecks.

How to verify

1. Deploy the updated sync-to-x configuration.
2. Initiate a data recording session that triggers the synchronization process.
3. Observe the system resource usage and ensure there are no slowdowns or hangs associated with NFS file checks.
4. Check the transfer speeds with both a NAS and an external SSD to confirm the bandwidth limit fix is working as expected (up to 200m).

Improvements

• Eliminates NFS-related slowdowns by removing the fuser dependency.
• Improves the flexibility of the synchronization service by making the mtime threshold configurable.
• Resolves previous transfer bandwidth limitations, allowing for faster data synchronization to external devices (NAS and SSD).

Limitations

• None identified.

[otenim]

Request: fix stat failure fallback in the active-file check

file_mtime=$(stat -c %Y "$mcap_file" 2>/dev/null || echo 0)
now=$(date +%s)
if [ $((now - file_mtime)) -lt {{ sync_to_x_active_file_threshold_sec }} ]; then
    continue
fi

When stat fails, file_mtime falls back to 0, so now - 0 is a huge number and the condition is false — the file is not skipped and the script proceeds to rsync, then rm -f on success.

Could you change the fallback to skip on stat failure instead? e.g.

if ! file_mtime=$(stat -c %Y "$mcap_file" 2>/dev/null); then
    echo "Skipping (stat failed): $mcap_file"
    continue
fi
now=$(date +%s)
if [ $((now - file_mtime)) -lt {{ sync_to_x_active_file_threshold_sec }} ]; then
    echo "Skipping recently modified file (active within {{ sync_to_x_active_file_threshold_sec }}s): $mcap_file"
    continue
fi

The file will be retried on the next timer tick, which is the safer default.

[citruscosmos]

@otenim
Thank you for the feedback! I have addressed the issue and confirmed that the nominal case is working as expected.
If there are no further concerns, could you please go ahead and merge this?