lend markets/rates --chain and --asset not marked as required cobra flags

[silicon-intern]

Problem

The lend markets and lend rates commands validate --chain and --asset manually in the RunE handler (via parseChainAsset), but the flags are not marked as required using MarkFlagRequired. This means:

1. defi lend markets --help doesn't show these flags as required
2. defi schema lend markets doesn't reflect them as required in machine-readable output
3. Error messages are less standard — cobra gives a clear required flag(s) "chain" not set vs the current custom error

Compare with bridge quote which correctly calls MarkFlagRequired for --from, --to, and --asset.

Suggested Fix

Add _ = marketsCmd.MarkFlagRequired("chain") and _ = marketsCmd.MarkFlagRequired("asset")) (and same for ratesCmd) in newLendCommand() in internal/app/runner.go.

Similarly, --protocol is validated manually but could also be marked required.