ClearChat Home v1.4.0 - Workflow Reliability Release

Fixes:
- Rebuilt Settings avatar upload as a separate upload workflow.
- Adds clear avatar upload errors instead of silent failure.
- Saves uploaded avatars to /uploads/avatars/ and updates Agent Avatar URL automatically.
- Rebuilt ZIP updater with stronger upload, extraction, permission, and ZIP-structure checks.
- Adds visible updater errors for unwritable files/folders.
- Adds update preflight checks.
- Adds pre-update database backup attempt.
- Adds Reliability menu link.
- Adds migration groundwork for audit log and backup records.

Notes:
- The web server user must be able to write to the ClearChat folder for in-app updates.
- On Ubuntu/Apache this is usually: sudo chown -R www-data:www-data /path/to/clearchat
