feat: auto-refresh contract state every 30s and wire landlord release action

[arandomogg]

Summary

• Resolves merge conflicts in app/escrow/[contractId]/page.tsx and lib/stellar/queries.ts, restoring all previously missing query infrastructure (getLandlord, getTotal, getDeadline, etc.) alongside both getContractState and getFeeStats.
• Creates hooks/useContractPolling.ts: polls getContractState every 30 s via setInterval; pauses automatically when the browser tab is hidden via visibilitychange; cleans up on unmount.
• Replaces the mock fetchData in EscrowDashboardClient.tsx with the new polling hook and adds an inline error/retry state.
• Refactors lib/stellar/actions/release.ts: fixes the stale window.freighter guard to use freighterApi.isConnected(), and splits the flow into buildReleaseXdr (assert funded + simulate) and signAndSubmitRelease (Freighter sign + Horizon submit); the original releaseEscrow convenience wrapper is kept.
• Adds a Release Funds button in EscrowDashboardClient.tsx that renders only when isConnected && publicKey === landlord; clicking it builds the prepared XDR, opens the TransactionReview security modal, then signs and submits on confirm, shows a "Funds released to landlord." toast, and refreshes state.

Test plan

• Confirm useContractPolling calls getContractState on mount and again after 30 s (mock two RPC responses and advance fake timers).
• Confirm polling is skipped while document.visibilityState === "hidden" and fires immediately when the tab becomes visible.
• Confirm the Release Funds button is absent for non-landlord wallets and present for the landlord wallet.
• Mock buildReleaseXdr + signAndSubmitRelease; confirm success toast and state refresh on confirm.
• Confirm the modal cancel path clears error and XDR state without submitting.

closes Ogstevyn#501
closes Ogstevyn#502

[arandomogg]

Opening against the correct upstream repo Ogstevyn/payeasy instead.