feat(records): unify tagging system to use string usernames and integrate suggestions endpoint

Title (semantic)

feat(records): persist hashtags and tagged usernames across upload, edit, and refresh

Description

This merge request implements persistent hashtag and tagged username support for records in the backend.

Changes Included

• Added support for saving hashtags and tagged_usernames in record schemas.
• Ensured tags entered during upload are stored correctly in the backend.
• Fixed issue where tags appeared after edit/save but disappeared after page refresh.
• Improved record update flow to preserve hashtags during record edits.
• Added backend handling for tag parsing and persistence.
• Updated upload validation schema to support hashtag/tagged user data.
• Improved record retrieval response to include saved tags consistently.
• Fixed backend behavior affecting frontend tag rendering after refresh.
• Added stability improvements for upload finalize flow and metadata persistence.

Checklist

• The feature has been fully implemented.
  • Tests for the new feature are included and passing.
  • User documentation/guides have been updated (if applicable).
  • Impact on existing functionality has been considered.
  • Existing upload and record flows remain backward compatible.
  • Tag persistence validated for upload, edit, and refresh scenarios.

Impact on Existing Functionality

• Existing record upload functionality remains unchanged.
• Additional metadata fields (hashtags, tagged_usernames) are now persisted.
• Improves frontend consistency by ensuring saved tags remain visible after reload.
• No breaking API changes introduced.

Related Issue(s)

Closes #<issue-number>

Testing Performed

• Uploaded records with hashtags and tagged usernames.
• Edited records and verified tag persistence.
• Refreshed record detail pages to confirm tags remain visible.
• Verified API response includes stored tag fields.
• Confirmed compatibility with existing record schema.

Backend Files Updated

• app/api/v1/endpoints/records.py
• app/schemas/upload_validation.py
• app/schemas/__init__.py
• app/models/record.py
• Related upload/tag persistence handling logic.