feat: add Linea USD (USDL) metadata on Linea

[alainncls]

Summary

• Add CAIP-19 metadata for Linea USD (USDL) on Linea (eip155:59144).
• Add the official, local SVG icon for the verified ERC-20 contract.

Verification

• Token contract: https://lineascan.build/token/0x91C4596B9Aba38CB46318F01A0C1943922f47aE5#transactions
• Project: https://linea.build/
• LI.FI listing: https://github.com/lifinance/customized-token-list/blob/6eca99fb4389558a0f257faeda0de2270679c5ca/tokens/LNA.json#L123

Test plan

• yarn asset:verify -- --caip eip155:59144/erc20:0x91C4596B9Aba38CB46318F01A0C1943922f47aE5
• node buildindex.js
• yarn test

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Note

Low Risk
Static metadata and icon only; no application or on-chain logic changes.

Overview
Adds Linea USD (USDL) to the asset catalog for Linea (eip155:59144/erc20:0x91C4596B9Aba38CB46318F01A0C1943922f47aE5).

New CAIP-19 metadata records the token as USDL with 6 decimals, and a paired local SVG logo under icons/ matches the usual Linea ERC-20 entry layout.

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