Add --exclude-unpriced flag to sim evm balances (GRO-229)

[ivpusic]

Summary

• New boolean flag --exclude-unpriced on dune sim evm balances (and, via shared addBalanceFlags, on dune sim evm stablecoins)
• Defaults to true, so tokens without a USD price are filtered out by default
• Pass --exclude-unpriced=false to include unpriced tokens
• Value is always forwarded as the exclude_unpriced query param so the CLI default stays pinned regardless of Sim API defaults

Test plan

• go build ./... clean
• go test ./cmd/sim/evm/... green
• Live Sim API, limit=50, chain 1, vitalik.eth: default returns 11 priced entries / 0 unpriced; --exclude-unpriced=false returns 42 entries (11 priced + 31 unpriced like ANON, LYRA, iPhone15 with no price_usd field)
• sim evm stablecoins --help shows the new flag

[cursor]

PR Summary

Low Risk
Small, CLI-only change that adds a new query parameter and tweaks default filtering behavior; no auth, writes, or sensitive data handling.

Overview
Adds a new --exclude-unpriced boolean flag to dune sim evm balances (and the shared stablecoins command flags) to control whether tokens lacking a USD price are returned.

The CLI now defaults to excluding unpriced tokens and always forwards the explicit exclude_unpriced=true|false query parameter to the Sim API to keep behavior consistent regardless of server defaults.

^{Reviewed by Cursor Bugbot for commit 02424c8. Configure here.}