feat(wallet): add Freighter connect button and page

[usmanimamu17-create]

Summary

Adds a Freighter wallet connect button to the frontend and the /connect-wallet page that the navbar already links to. The button lets a user connect, see their active account address, and disconnect, and it restores the previously connected address after a page reload.

Problem

The navbar linked to /connect-wallet, but that route did not exist, so clicking "Connect Wallet" led to a missing page. There was a useWalletConnection hook with the wallet lifecycle logic, but no user-facing control wired to it, and nothing displayed the active account address. A connected session was also lost on every reload.

Changes Made

• Added frontend/components/WalletConnectButton.jsx: a reusable control built on the existing useWalletConnection hook. It renders a "Connect Wallet" button while disconnected, shows the shortened active address with a "Disconnect" button once connected, displays a spinner while connecting, surfaces the hook's rejection/extension error, and persists the connected address in localStorage so a reload keeps showing the active session.
• Added frontend/app/connect-wallet/page.tsx: the page the navbar links to, rendering the connect button.

Implementation Details

The button delegates all wallet operations to useWalletConnection, so user rejection and a missing extension are handled by the hook and shown inline via its error value. The connected address is mirrored to localStorage under stellarhunts.wallet.address on connect and cleared on disconnect so the session survives reloads. The display shortens the public key (GABC...WXYZ) while keeping the full address available via the title attribute.

Closes #686

Closes #688

Closes #689

Closes #691

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[dzekojohn4]

LGTM