refactor: remove RainbowKit and replace with custom wagmi wallet modal

[kushbosamiya]

Overview

Remove @rainbow-me/rainbowkit and all related third-party wallet modal UI
dependencies from the Fate EVM Frontend. Replace with a fully custom,
lightweight wallet connection system built directly on wagmi primitives to
fix Framer Motion style overrides, reduce bundle weight, and give full UI
control over the connect/disconnect/network-switching experience.

---

Problem

• @rainbow-me/rainbowkit injects global CSS that conflicts with Framer Motion
  animations used elsewhere in the app.
• The RainbowKit modal overrides layout styles and introduces unpredictable
  z-index and positioning bugs.
• Heavy bundle footprint from an opinionated UI library for a use case we
  can own entirely with wagmi hooks.
• No control over modal design, connector ordering, or network mismatch UX.

---

Solution

Replace RainbowKit with a local custom wallet UI that:

• Uses wagmi hooks directly (useAccount, useConnect, useDisconnect,
  useChainId, useSwitchChain)
• Renders a fully custom animated connect modal with local wallet logos
• Handles all wallet states — disconnected, connecting, connected,
  wrong network, unknown network
• Implements explicit chain switching from both UI and wallet side
• Adds structured event logging for every wallet interaction

---

Changes

Area	Change
package.json	Remove @rainbow-me/rainbowkit and related packages
providers/providers.tsx	Remove RainbowKitProvider wrapper
app/layout.tsx	Remove RainbowKit stylesheet import
lib/wallets.ts	Add connector → logo/name mapping utility
lib/chains.ts	Add supported chain registry and validation helpers
lib/walletLogger.ts	Add structured wallet event logger
hooks/useWalletConnection.ts	Add unified wallet state + actions hook
hooks/useChainChangeWatcher.ts	Add external chain change detection hook
components/ui/ConnectBtn.tsx	Rebuild with custom modal, all wallet states
components/ui/ChainSwitcher.tsx	Add network switcher UI component
public/wallets/	Add local wallet logo assets

---

Wallet States Covered

• Disconnected — Connect Wallet button, animated connector list modal
• Connecting — Per-row loading spinner, inline error on rejection
• Connected / Correct Network — Address badge, chain name, account modal
• Connected / Wrong Network — Warning badge, switch network CTA
• Connected / Unknown Network — "Unknown Network" label, chain ID display

---

Acceptance Criteria

• npm run lint passes with 0 errors
• No imports from @rainbow-me/rainbowkit remain anywhere
• Connect → approve → address shows correctly
• Reject in wallet → modal stays open, error shown inline
• Switch chain from UI → wallet prompts → UI updates reactively
• Switch to unsupported chain from wallet → "Wrong Network" renders
• Switch to unknown chain → "Unknown Network" renders with chain ID
• All wallet events log in [WALLET][EVENT_NAME] format in dev
• Pool interaction, buy/sell, and rebalance flows are unaffected
• No Framer Motion style conflicts remain

---

References

• Related PR in IdentityTokens: StabilityNexus/IdentityTokens-EVM-Frontend#92
• wagmi docs: https://wagmi.sh