Add swap service

[watersRand]

Description

This PR introduces the SIM Swap Detection Service (/imsi/v2/checkATI) to support checking when a subscriber's SIM card was last swapped. This helps detect and mitigate account takeover and fraud risks prior to completing high-value transactions.

Key changes included:

• Service & Facades: Implemented SwapService and AsyncSwapService with swap_query(customer_number) and swap_request(request) methods.
• Data Validation & Schemas: Added SwapRequest (with MSISDN auto-normalization) and SwapResponse Pydantic models.
• Fraud Detection Helpers: Added is_successful and is_recently_swapped properties to SwapResponse to handle Safaricom's sentinel non-swapped date (01-01-1900).
• Type Stubs & Documentation: Added .pyi type stubs, updated docs/swap.md, and updated landing page status/feature data.

Fixes #160

Type of Change

• New feature (non-breaking change that adds functionality)
• This change requires documentation update

How Has This Been Tested?

• Unit Tests: Added tests covering SwapRequest phone number auto-normalization, SwapResponse.is_recently_swapped sentinel date evaluation (01-01-1900 vs active timestamp), and sync/async service call execution.
• Ruff & Type Linting: Executed ruff check and type assertions with .pyi stub files to verify clean linting across the package.

Checklist

• My code follows the project's coding style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

N/A (Backend API addition & documentation update)

Additional Context

• SIM Swap Detection (checkATI) is a paid API product on Safaricom Daraja. Documentation and docstrings reflect onboarding guidance for sandbox and production.

[RafaelJohn9]

Hello @watersRand , thanks for the awesome PR, a few changes to consider 🤝

[RafaelJohn9]

Apologies for the late review. you can always tag me for a review, no worries 🤝 ,

Thanks for the changes and we have a few things to do before we become ready to merge.

• Remove the environment parameter across the Swap module since this is only used inside http_client module.
• We then update the stubs correctly.
• Then we wire in this service to client and async client see (https://github.com/Byte-Barn/mpesakit/blob/master/mpesakit/mpesa_client.py)

Then we will be good to go 👍

[RafaelJohn9]

We can deprecate the environment parameter that we have across the different swap files, since this is handled by our http client file.

[watersRand]

@RafaelJohn9 ready