Adopt branded zod schemas across lend/swap/wallet controllers

[its-everdred]

PR #465 introduced shared branded zod helpers in packages/demo/backend/src/helpers/schemas.ts:

• AddressSchema — validates 0x[a-fA-F0-9]{40} and lowercases the value before branding as Address.
• Bytes32Schema — validates and lowercases bytes32.
• ChainIdSchema / ChainIdStringSchema — accepts number or numeric string, brands as SupportedChainId.
• BorrowAmountRawSchema — bigint-as-decimal-string capped at .max(78) to bound DoS surface.

These live in helpers/schemas.ts so lend/swap/wallet can share them. Today only borrow consumes them; the rest still use raw regex or ad-hoc transforms:

• controllers/wallet.ts:32 (/wallet/eth/...) — raw regex on address, no lowercase normalization.
• controllers/lend.ts — request shapes use bespoke validators.
• controllers/swap.ts — request shapes use bespoke validators.

Acceptance

• Replace ad-hoc address validation in controllers/wallet.ts, controllers/lend.ts, controllers/swap.ts with AddressSchema from helpers/schemas.ts.
• Replace ad-hoc chainId parsing with ChainIdSchema / ChainIdStringSchema where appropriate.
• Apply BorrowAmountRawSchema (or a renamed AmountRawSchema) to lend/swap amount fields if currently uncapped strings.
• If we rename for breadth, update borrow consumers in the same PR.
• Add tests confirming mixed-case input is normalized at the boundary.