Replace all `any` types with specific types

## Problem

There are ~51 `@typescript-eslint/no-explicit-any` warnings across the SDK and demo backend. Using `any` bypasses type checking and can hide bugs.

## Scope

**SDK source files:**
- `lend/providers/aave/sdk.ts`
- `lend/providers/morpho/api.ts`
- `lend/providers/morpho/sdk.ts`
- `services/__mocks__/MockChainManager.ts`

**SDK test files:**
- `lend/core/__tests__/LendProvider.test.ts`
- `lend/providers/morpho/__tests__/MorphoLendProvider.test.ts`
- `services/tokenBalance.spec.ts`
- `swap/providers/uniswap/__tests__/sdk.test.ts`
- `utils/assets.test.ts`
- `wallet/react/wallets/hosted/dynamic/__tests__/DynamicWallet.spec.ts`
- `wallet/react/wallets/hosted/privy/__tests__/PrivyWallet.spec.ts`
- `wallet/core/wallets/smart/default/__tests__/DefaultSmartWallet.spec.ts`

**Demo backend:**
- `packages/demo/backend/src/helpers/validation.spec.ts`
- `packages/demo/backend/src/services/lend.spec.ts`
- `packages/demo/backend/src/services/swap.spec.ts`

## Guidelines

Follow existing patterns in the codebase:

- **External API responses** — use `unknown` and narrow with type guards or assertions, not `any`. See `utils/assets.ts` for examples of typed return values.
- **Mock objects in tests** — use `as unknown as SpecificType` instead of `as any`. See `swap/__mocks__/MockSwapProvider.ts` for the pattern:
```ts
const publicClient = { readContract: vi.fn() } as unknown as PublicClient
```
- **Generic callbacks and parameters** — use `unknown` with type narrowing, or define a proper generic. Prefer `Record` over `Record`.
- **viem contract call returns** — cast to the expected tuple type. See `encoding/v2.ts`:
```ts
return (amounts as bigint[])[1]
```
- **Error handling** — use `unknown` for catch parameters:
```ts
catch (error: unknown) { ... }
```
- **JSON/API data** — define response interfaces rather than using `any`. See `types/swap/base.ts` and `types/lend/base.ts` for examples.

## Verification

After replacing all `any` types, `pnpm lint` should show 0 `no-explicit-any` warnings. Run `pnpm typecheck` to confirm no type errors were introduced.

Start by running pnpm lint and reviewing the listed SDK, test, and demo backend files, using utils/assets.ts, swap/__mocks__/MockSwapProvider.ts, encoding/v2.ts, and the lend and swap type files as reference. Replace the scoped any usages according to the existing patterns, then confirm pnpm lint reports zero no-explicit-any warnings and pnpm typecheck passes.

Written by the indexing model from the issue text.