refactor: extract generic fetchAllPaginated helper

[ArchiDevil]

Summary

All list endpoints (, , , , , ) had the same ~40-line pagination boilerplate: get count → loop with sequential → concat → map types.

Extracted a generic fetchAllPaginated<DirectusT, ApiT> helper that:

• Centralizes pagination logic in one place (server/utils/fetchAllPaginated.ts)
• Uses Promise.all instead of sequential requests — pages fetch in parallel
• Reduces each endpoint to config + mapper (~15 lines)

Changes

File	Before	After
spells.ts	53 lines	33 lines
feats.ts	50 lines	24 lines
backgrounds.ts	50 lines	27 lines
magic-items.ts	63 lines	34 lines
facilities.ts	52 lines	27 lines
spell-cards.ts	113 lines	93 lines
fetchAllPaginated.ts	—	30 lines
Total	381	268

Net -113 lines, and adding a new list endpoint is now trivial.

Bonus

Also fixes the sequential-fetch performance issue (#5 from the code review) — all pages now fetch in parallel.