fix: use Fr.fromString for CLI wallet claim params to handle decimal values (#22197)

## Summary

Fixes incorrect parsing of `--payment` claim parameters in the CLI
wallet when using the explicit long form:
```
--payment method=fee_juice,claimAmount=123,claimSecret=0xabc,messageLeafIndex=42
```

**Bug**: `Fr.fromHexString()` was used to parse `claimAmount`, which
interprets bare numeric strings as hex. When a user copy-pastes the
output of `bridge-fee-juice` (which prints `claimAmount` as a decimal
bigint like `1000000000000000000`), it would be silently misinterpreted
as a hex value, resulting in a completely wrong claim amount.

**Fix**: Switch to `Fr.fromString()` which correctly auto-detects
decimal vs hex (0x-prefixed) input. Also adds a type guard for
`claimSecret` to handle both the DB path (which returns a string) and
the direct CLI path uniformly.

## Changes

- `Fr.fromHexString(claimAmount)` → `Fr.fromString(claimAmount)` —
handles decimal amounts correctly
- `Fr.fromHexString(claimSecret)` → `Fr.fromString(claimSecret)` with
type guard — consistent handling for both DB and CLI paths

## Test plan

- Verify `deploy-account --payment
method=fee_juice,claimAmount=1000000000000000000,claimSecret=0xabc...,messageLeafIndex=42`
correctly parses the decimal amount
- Verify `deploy-account --payment method=fee_juice,claim` (DB-backed
short form) still works unchanged
- Verify hex-prefixed values like `claimAmount=0x1234` still work
correctly

ClaudeBox log: https://claudebox.work/s/7737b856f8012542?run=2

Author: Thunkar

yarn-project/cli-wallet/src/utils/options/fees.ts

@@ -158,10 +158,10 @@ export function parsePaymentMethod(
           const { FeeJuicePaymentMethodWithClaim } = await import('@aztec/aztec.js/fee');
           return new FeeJuicePaymentMethodWithClaim(from, {
             claimAmount: (typeof claimAmount === 'string'
-              ? Fr.fromHexString(claimAmount)
+              ? Fr.fromString(claimAmount)
               : new Fr(claimAmount)
             ).toBigInt(),
-            claimSecret: Fr.fromHexString(claimSecret),
+            claimSecret: typeof claimSecret === 'string' ? Fr.fromString(claimSecret) : claimSecret,
             messageLeafIndex: BigInt(messageLeafIndex),
           });
         } else {