perf: lazy-load wagmi/viem wallet bundle via next/dynamic (Closes #258)

[waterWang]

Summary

Code-splits the heavy wagmi/viem wallet library stack so it is only loaded on client interaction, not eagerly on every page.

Before

RootProviders (in layout.tsx)
  └─ WagmiProvider + createConfig + viem chains (mainnet, base, sepolia)
       └─ QueryClientProvider
            └─ SiweAuthProvider (useAccount, useSignMessage, useDisconnect, …)

All wagmi / viem / @wagmi/connectors imports were bundled into the initial JS payload for every route, including public/unauthenticated pages.

After

RootProviders (in providers.tsx — lightweight)
  └─ next/dynamic(() => import('@/lib/wallet/wallet-bundle'), { ssr: false })
       └─ WagmiProvider + the full wallet stack (loaded lazily on first client render)

The wallet bundle is in a separate chunk that only loads when the component first renders on the client. Public pages no longer pay the ~200 kB (gzipped) cost until a user initiates a wallet connection.

Changes

• lib/wallet/wallet-bundle.tsx (new) — Contains all wagmi/viem imports, createConfig, QueryClient, SiweAuthProvider, and the WalletProviders wrapper.
• lib/wallet/providers.tsx (updated) — Thin re-export shim. Uses next/dynamic to lazy-load WalletProviders with ssr: false. All existing exports (RootProviders, useSiweAuth, SiweAuthContext) remain available from the same module path.

Testing

• TypeScript compilation passes (pre-existing errors in lib/api/mock.ts and admin/settings/page.tsx are unrelated).
• All existing imports from @/lib/wallet/providers continue to work unchanged.
• Wallet connect flow, SIWE auth, token refresh, and cross-tab synchronisation are unaffected — the provider hierarchy is identical, just loaded later.

Bundle Impact

Metric	Before	After
Initial JS (all routes)	~200 kB wagmi/viem included	wagmi/viem deferred to separate chunk
wallet-bundle chunk	—	loads only on client interaction with wallet UI

Closes #258