Refund Logic Implementation

[AkibDa]

fix: correct Firestore batch update in cancel order flow

• Fixed incorrect batch.update usage causing 500 error
• Properly separate order and user updates in batch
• Refund, resale, and staff payout logic now executes correctly

feat: add idempotency protection for payments and cancellations

• Prevent double refunds on order cancellation
• Make payment verification idempotent
• Harden Razorpay webhook handlers against retries

[github-advanced-security]

Prospector (reported by Codacy) found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[github-advanced-security]

Pylintpython3 (reported by Codacy) found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[github-advanced-security]

Pylint (reported by Codacy) found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.