Fix CHIP-0002 precision

[Rigidity]

Note

Medium Risk
Changes the WalletConnect API contract for coin/lineage amounts from u64/number to an Amount (number-or-string) representation, which can impact external clients and parsing of incoming spend bundles.

Overview
Fixes CHIP-0002 precision issues by switching WalletConnect coin amounts to the shared Amount type (string-or-number) instead of plain u64/JS number.

Backend endpoints now emit amounts via Amount::u64(...) and consume them by converting Amount back to u64 with validation/erroring on invalid values. Frontend bindings and WalletConnect command Zod schemas were updated to accept amount as number | string, and locale message source line references were refreshed due to unrelated file shifts.

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