[Bug] ReaderPortfolio scans all storylines for balanceOf — N+1 scaling

[realproject7]

Bug

src/components/ReaderPortfolio.tsx fetches every non-hidden storyline from the DB, then calls balanceOf() for each one to check if the user holds tokens. With N storylines, this is N RPC calls just to find holdings.

Impact: Does not scale. With 100+ storylines, the reader dashboard becomes very slow.

Fix options:

1. Use viem multicall to batch all balanceOf checks into a single RPC call
2. Add a subgraph or indexer for token holdings (heavier lift)
3. At minimum, add caching with a reasonable TTL

Context: Introduced in PR #87.

Checklist:

• Batch balanceOf calls using multicall
• npm run lint and npm run typecheck pass

Labels: bug, agent/T3