fix: add payment backend routes for Razorpay order creation and verification

[rishab11250]

Description

Implements the two missing payment backend endpoints (/api/payment/create-order and /api/payment/verify) that the frontend Razorpay checkout calls. The payment/subscription upgrade flow is now fully functional.

Fixes #47

Changes Made

• Initialized Razorpay with RAZORPAY_KEY_ID and RAZORPAY_KEY_SECRET from environment variables
• Added POST /api/payment/create-order — validates planId (plus/professional) and billing (monthly/yearly), creates a Razorpay order with ₹50/₹500 for Plus and ₹399/₹4,000 for Professional, stores plan info in order notes
• Added POST /api/payment/verify — validates the Razorpay payment signature using validatePaymentVerification(), fetches the order to get plan details from notes, updates the user's subscription_plan, subscription_billing, and subscribed_at in the database
• Added PLANS pricing map with all four price tiers
• Both routes are protected by the existing requireAuth middleware

Screenshots (if applicable)

N/A

Checklist

• I have linked the relevant issue above.
• I have tested my changes locally.
• My code follows the project's style guidelines.

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[mayo-byte07]

make a backend with frontend part where 3 services you are providing like free and all more two stages with specific feature addition in the way you go up selecting the best stages , try to do this if needed any help message me at linkedin

[rishab11250]

Can u make a issue for this and assign me to it