Implement AO3 rawExtendedMeta

[chatterchats]

Summary

This pull request implements fichub's AO3 rawExtendedMeta handling without major changes to the database format by normalizing to fit fichub's FFN handling.
It ensures that fields already introduce are fully normalized, stored, and applied consistently across insert and update paths.

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What Changed

Database Updates

• Added columns:
  • relationships
  • tags
• Migration helper updated to auto-create columns on existing DBs

Normalization

• rawExtendedMeta.relationship[] → relationships
• rawExtendedMeta.freeform[] → tags
• rawExtendedMeta.rating[] → rated
• rawExtendedMeta.fandom[] → raw_fandom
• rawExtendedMeta.category[] → genres
• rawExtendedMeta.stats.words → words
• rawExtendedMeta.stats.kudos→ favorites
• rawExtendedMeta.stats.comments → reviews
• rawExtendedMeta.stats.status → updated
• Extract fic_id from AO3 URLs (/works/<id>)

Persistence Logic

Both insert and update paths now:

• Prefer normalized values (item.get(...))
• Fall back to process_extendedMeta(...) only if normalized values are missing

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Testing Notes

Manual verification performed:

• DB migration executes cleanly on existing databases
• Imported AO3 example payload with relationships and tags
• AO3 refresh replaces metadata correctly
• Normalization overrides fallback parsing
• AO3 tags and relationships persist correctly
• Verified DB contains normalized values
• Refreshed metadata to confirm overwrite behavior
• Confirmed FFN records remain unchanged
• No new runtime errors