### What problem does this PR solve?
Feat: enable sync deleted files for Gmail && fix google drive issues
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
---------
Co-authored-by: bill <yibie_jingnian@163.com>
Co-authored-by: balibabu <assassin_cike@163.com>
### What problem does this PR solve?
Feat: enable sync delted files for connectors
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
Closes https://github.com/infiniflow/ragflow/issues/13939
## What problem does this PR solve?
The Google Drive connector fails to detect new files after the initial
sync (#13939). The root cause is that `generate_time_range_filter()`
applies a strict `modifiedTime > poll_range_start` cutoff when querying
the Google Drive API. Files uploaded to Google Drive that retain their
original `modifiedTime` (common behavior) get silently excluded if their
timestamp predates the last sync's cutoff.
Unlike the Confluence and Jira connectors which use a configurable time
buffer (`CONFLUENCE_SYNC_TIME_BUFFER_SECONDS`) to offset
`poll_range_start` backward, the Google Drive connector had no such
mechanism — resulting in a razor-sharp timestamp boundary with zero
tolerance for overlap.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
## Summary
* **New Features**
* Added a configurable time buffer for Google Drive synchronization to
address timing delays and improve sync reliability.
* Improved file detection logic to include recently created files
alongside modified ones, reducing missed synchronizations.
### What problem does this PR solve?
- Add license
- Fix IDE warnings
### Type of change
- [x] Refactoring
---------
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>
### What problem does this PR solve?
_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
