docs: add CLI manual testing guide for contributors #77

[Code-Paragon]

Title: docs: add CLI manual testing guide for contributors #77

Description

This PR Closes #77 by adding a comprehensive, step-by-step CLI manual testing guide (docs/cli-testing-guide.md) for external contributors and core developers.

The guide details the end-to-end flow for:

• Setting up local Testnet environments and generating testing identities.
• Compiling optimized WASM binaries using the existing Makefile.
• Deploying and invoking the invoice_nft contract (including set_backend_pubkey, mint, and repay workflows).
• Deploying and invoking the tradeflow factory contract (including initialize_factory, create_pool, and pair_exists).

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (non-breaking change to add/improve docs)

Testing Strategy

• Verified the accuracy of contract function names (initialize_factory, create_pool, mint, get_invoice, repay) against the current implementations in contracts/tradeflow/src/lib.rs and contracts/invoice_nft/src/lib.rs.
• Checked parameter signatures to ensure inputs match the expected XDR types (Addresses, BytesN, i128, etc.).
• Validated Stellar CLI syntax and flags for --source, --network testnet, and contract invocations.

Self-Review Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own work
• I have commented my work, particularly in hard-to-understand areas
• My changes generate no new warnings or formatting errors

[AlAfiz]

@Code-Paragon Good code