### What problem does this PR solve?
Fixes [#13505](https://github.com/infiniflow/ragflow/issues/13505): Jira
incremental sync could miss updated issues after initial sync,
especially near time boundaries.
Root cause:
- Jira JQL uses minute-level precision for `updated` filters.
- Incremental windows had no overlap buffer, so boundary updates could
be skipped.
- Sync log cursor tracking used a backward-facing update for
`poll_range_start`.
- Existing-doc updates in `upload_document` lacked a KB ownership guard
for doc-id collisions.
What changed:
- Added Jira incremental overlap buffer (`time_buffer_seconds`,
defaulting to `JIRA_SYNC_TIME_BUFFER_SECONDS`) when building JQL
lower-bound time.
- Preserved second-level post-filtering to avoid duplicate reprocessing
while still catching boundary updates.
- Improved Jira sync logging to include start/end window and overlap
configuration.
- Updated sync cursor tracking in `increase_docs` to keep
`poll_range_start` moving forward with max update time.
- Added KB ID safety check before updating existing document records in
`upload_document`.
Verification performed:
- Python syntax compile checks passed for modified files.
- Manual verification flow:
1. Run full Jira sync.
2. Edit an already-indexed Jira issue.
3. Run next incremental sync.
4. Confirm updated content is re-ingested into KB.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
---------
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
