feat: wire seller confirmation to approve-milestones (#310)

[Killerjunior]

📝 feat: Wire seller confirmation to approve-milestones (#310)

🛠️ Issue

• Closes Wire seller confirmation to POST /escrow/single-release/v2/approve-milestones #310

📖 Description

• Connects the seller confirmation flow in /p2p/chat when accepting a payment request after a buyer marks a milestone as completed.
• Calls POST /escrow/single-release/v2/approve-milestones with { contractId, approver: sellerAddress, milestoneIndexes: [0] }.
• Prompts the seller's wallet (e.g., Freighter) to sign the returned unsignedXdr and submits the signed transaction via POST /escrow/send-transaction.
• Updates the UI status to "approved, ready for release" once the transaction is confirmed.

✅ Changes made

• lib/trustless-work.ts: Added approveMilestones and sendTransaction endpoints to trustlessWork.escrow alongside the signAndSendTransaction helper.
• frontend/components/PaymentBubble: Updated status types and UI rendering to enable the accept button only when the milestone is completed by the buyer, and added the "approved, ready for release" state display.
• frontend/components/chat/types.ts: Updated PaymentStatus and PaymentRequestMessage interface to include contractId and sellerAddress.
• app/p2p/chat/page.tsx: Created the /p2p/chat page implementing the full seller confirmation, wallet signing, and state update pipeline.

🖼️ Media (screenshots/videos)

📜 Additional Notes

• The action is disabled until the milestone status is marked as completed from the buyer's side.
• Installed @stellar/freighter-api to enable wallet transaction signing integration.

[diegoTech14]

Hello @Killerjunior could you upload images or video evidence please?

[Killerjunior]

Noted. Uploading now.

[Killerjunior]

Screenshots have been added in the PR description as well as walkthrough.md file. Kindly review once more.

[diegoTech14]

Hi @Killerjunior could you resolve conflicts please?