feat(partnerships): add create_account MCP tool for sub-merchant onboarding

[rzp-slash]

Summary

Adds the create_account MCP tool for Razorpay's Partnerships Onboarding API, enabling partner agents to onboard sub-merchants programmatically.

• Adds pkg/razorpay/accounts.go with the CreateAccount tool (POST /v2/accounts)
• Registers a new partnerships toolset in pkg/razorpay/tools.go
• Uses the existing client.Account.Create from the razorpay-go SDK (already supports v2)

Tool: create_account

Required: phone

Optional: email, legal_business_name, business_type, contact_name, customer_facing_business_name, reference_id, type, profile (category + subcategory + addresses), legal_info (pan/gst/cin), brand (hex color without #), notes, contact_info (chargeback/refund/support/dispute), apps (websites/android/ios)

Field validations sourced directly from razorpay/partnerships validator:

• phone is a string (not number), validated via IsPhoneNumber
• business_type enum matches the partnerships service constants exactly
• brand.color is 6-char hex WITHOUT # prefix (^[0-9a-fA-F]{6}$)
• contact_info has 4 sub-fields: chargeback, refund, support, dispute
• profile.addresses.registered is required when profile is provided

Test plan

• create_account tool appears in the partnerships toolset
• Calling with only phone succeeds (only required field)
• Calling with full payload (profile + legal_info + brand + contact_info) succeeds
• Invalid business_type returns API-level validation error from Razorpay
• brand.color with # prefix returns error from Razorpay API

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 1.79910% with 655 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.62%. Comparing base (7950d51) to head (18f920c).

Files with missing lines	Patch %	Lines
...g/razorpay/partnerships/onboarding_apis/account.go	0.00%	410 Missing ⚠️
...g/razorpay/partnerships/onboarding_apis/helpers.go	0.00%	109 Missing ⚠️
pkg/razorpay/partnerships/auth/token.go	0.00%	84 Missing ⚠️
pkg/razorpay/partnerships/auth/helpers.go	0.00%	51 Missing ⚠️
cmd/razorpay-mcp-server/stdio.go	0.00%	0 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (1.79%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #102      +/-   ##
==========================================
- Coverage   97.35%   89.62%   -7.73%     
==========================================
  Files          35       39       +4     
  Lines        7567     8233     +666     
==========================================
+ Hits         7367     7379      +12     
- Misses        136      790     +654     
  Partials       64       64              

Flag	Coverage Δ
unittests	89.62% <1.79%> (-7.73%)	⬇️

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