feat(store): modularize global state into campaign/wallet/ui slices

[Darkdruce]

Summary

Splits the monolithic Zustand store into three independently-testable slices with scoped selector hooks, closing the source of unrelated re-renders and merge conflicts described in Fund-My-Cause#865.

Changes

New slice files

File	Responsibility
store/campaignSlice.ts	Transient campaign UI state: active campaign ID, optimistic contribution deltas, pledge modal flag, pledge amount draft
store/walletSlice.ts	Re-exports useWalletStore + named typed selectors
store/uiSlice.ts	Re-exports notification / modal / theme stores + named selectors per sub-domain
store/index.ts	Barrel — single import point for all slices and selectors

Scoped selector hooks

Hook file	Exported hooks
hooks/useCampaignSlice.ts	useCampaignSlice(), usePledgeModal(), useOptimisticDelta(id)
hooks/useWalletSlice.ts	useWalletSlice(), useWalletStatus(), useWalletSigning()
hooks/useUiSlice.ts	useUiSlice(), useNotifSlice(), useModalSlice(), useThemeSlice()

All hooks use useShallow to prevent re-renders when unsubscribed fields change.

Consumer migrations (no behaviour change)

• hooks/useWallet.ts → useWalletSlice()
• hooks/useModal.ts → useModalSlice()
• hooks/useNotifications.ts → useNotifSlice()
• components/ModalRenderer → useModalSlice()
• components/WalletSelectModalHost → useWalletSlice()

Backward compatibility

• All existing action names preserved (connectWith, disconnect, signTx, openModal, etc.)
• Direct store imports (useWalletStore, useModalStore, etc.) continue to work — nothing removed

Tests

• 67 new tests across three test files (campaignSlice.test.ts, walletSlice.test.ts, uiSlice.test.ts)
• Covers all reducers, actions, and selectors in isolation
• Existing useWallet.test.tsx (11 tests) remains green
• ESLint and Prettier hooks pass at commit time

What was tested

• npx tsc --noEmit — 0 errors in new files
• npx jest store/__tests__ — 67/67 pass
• npx jest hooks/useWallet.test — 11/11 pass

Closes Fund-My-Cause#865