Wire TopMoversCard to /api/v1/rankings/top-movers

[christabel888]

Context: Data plumbing for #42, depends on Stellar-Insightss/backend#33.

Where:

• src/services/api.ts
• New hook alongside useDashboardScreen.ts

What to do:

• Add a typed fetch for Add /api/v1/rankings/top-movers endpoint: 24h percent change by holders/volume backend#33's endpoint and wire it into TopMoversCard.

Suggested approach:

1. Backed by Stellar-Insightss/backend#33.

Watch out for:

• New assets with no 24h baseline need explicit handling on the client side too, matching backend Add asset allocation breakdown to Wallet Dashboard screen #33's edge-case work (Update screen titles per rename table across MainNavigator.tsx #38 there) -- don't assume the backend fully shields you from bad values.

Definition of done:

• TopMoversCard renders real ranking data