⚡ Bolt: optimize admin categories query

[bbaaxx]

💡 What: Optimized the admin categories list by replacing a redundant db.batch call and manual in-memory counting with a single SQL aggregation query using LEFT JOIN and GROUP BY. Additionally, fixed a schema mismatch in scripts/init-db.ts where the level column was missing from the moves table, causing home page crashes.

🎯 Why: The previous implementation fetched all categories and then all moves to merge them in the application layer, which is inefficient as the data grows. Offloading this to the database reduces network overhead and CPU usage. The schema fix ensures the local development environment correctly reflects the application's data requirements.

📊 Impact:

• Reduces database round-trips from multiple queries to one.
• Eliminates application-layer overhead for counting related records.
• Fixes critical runtime error on the home page for new local database setups.

🧪 Measurement: Verified via Playwright screenshots (confirming 0 and non-zero counts display correctly), pnpm lint, pnpm test:unit, and pnpm test:e2e.

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PR created automatically by Jules for task 17330098947948746916 started by @bbaaxx

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