General Onboarding - Updates the general onboarding cutoff mechanism

### Overview

We need to revise the logic of the general onboarding cut off mechanism to combine minutes of attendance per user so that users who attend 83%(50 mins) of the event (even when being disconnected and reconnected) get validated.

#### Details

This issue updates the general onboarding cutoff mechanism to implement a new attendance validation logic based on a total of 83%(50-minute) minimum duration and internet stability, ensuring accurate verification of volunteer participation. The updated mechanism will be reflected in the HFLA Volunteers spreadsheet and documented in General_Onboarding_Automation.md.

**without internet issues** = rejoin part1 on-boarding session less than twice
**internet issues** = rejoin part1 on-boarding session twice or more

**mechanism logic** :

Update the attendance validation logic in general_onboarding.gs to:

- Check "attn-verified" for attendees with ≥50 minutes without internet issues (e.g., 6:02–6:19 [18 min] + 6:20–6:53 [34 min] = 52 min, 96% of a 54-minute meeting).

- Uncheck "attn-verified" for attendees with ≥50 minutes but with internet issues (e.g., 6:02–6:08 [6 min] + 6:10–6:37 [27 min] + 6:40–6:53 [13 min] = 46 min, 87%), requiring manual override.

scenario that are already covered by current logic:
- Uncheck "attn-verified" for attendees with <50 minutes due to internet issues (e.g., 6:02–6:04 [2 min] + 6:10–6:18 [8 min] + 6:40–6:53 [13 min] = 23 min).

### Action Items
- [ ] Create a new branch (e.g., update-onboarding-cutoff) for implementation and version control with Clasp.

- [ ] Update ZoomAttendeeReport.gs to reflect the new cutoff logic in the "Part1_onboarding_zoom_attendee_report" spreadsheet.

- [ ] Update General_Onboarding_Automation.md to document the new cutoff mechanism with provided examples.

- [ ] Test the updated logic by simulating Zoom attendee reports with sample data (e.g., provided time ranges) to verify "attn-verified" and "attn-duration" fields.

- [ ] Submit a PR for code review, including changes to general_onboarding.gs, ZoomAttendeeReport.gs, and General_Onboarding_Automation.md.

### Resources/Instructions
- https://github.com/hackforla/tables/pull/126