fix(assets): resolve USDC price via primary-protocol fallback in transfer dropdowns

[metodi96]

Summary

Fix USDC (and other shared-IBC-denom assets) showing $0.00 and mis-sorting to the bottom of the Assets transfer modal's Swap/Deposit/Withdraw dropdowns despite a real balance. Closes #166.

The dropdowns priced each asset via pricesStore.prices[currency.key], where currency is resolved through tryGetCurrencyByDenom(denom). For a shared IBC denom (e.g. USDC), that denom-keyed map holds one arbitrary protocol entry (e.g. USDC@NEUTRON) whose key has no published price, so the value defaulted to 0. The main Assets table was unaffected because it resolves via the network's primary protocol, which is priced.

Changes

• Add getPriceForCurrency(currency) in CurrencyLookup.ts: returns the currency's own price, or — when its key is absent from the feed — falls back to the network's primary-protocol key for the same ticker (the same path the Assets table uses via getCurrencyByTickerForNetwork), before defaulting to "0". The direct != null check distinguishes "unpriced" from "genuinely priced at 0".
• Route all seven price lookups across the three forms through the helper — the dropdown asset lists and the amount estimators (calculatedBalance, firstCalculatedBalance, secondCalculatedBalance) — so the whole modal stays consistent, not just the dropdown listing.
• Remove the now-unused prices-store wiring from the three forms.
• Add CurrencyLookup.test.ts covering own-price, primary-protocol fallback, the double-miss "0" default, and the dropdown sort position for a held-balance asset whose denom-resolved key is unpriced.

Verification

• npx tsc --noEmit — passed
• npx prettier --check on changed files — passed
• npx eslint --max-warnings=0 on changed files — passed
• npx vitest run — 764 tests passed across 49 files (4 new regression tests added)
• Diff review (fresh-context) — PASS on the 12-item checklist and all acceptance criteria
• Security review — 0 critical / 0 high; 2 non-blocking notes (see below)

Notes

• The primary-protocol fallback matches by ticker, per the approach suggested in fix: USDC mis-sorted to bottom of Swap/Deposit/Withdraw asset dropdowns despite balance #166. This is correct for shared-denom stablecoins; it assumes same-ticker assets share a USD price, which holds for the affected assets. It is display-only and fires solely when the asset's own key is unpriced — route execution does its own quoting.