Test that get_stream returns the schedule exactly as provided

[Glittersup]

Summary

The schedule fields stored at creation are what every later calculation depends on, but nothing asserts that they round-trip unchanged. A test comparing the stored stream against the arguments passed to create_stream pins that down.

Acceptance criteria

• A test asserts the schedule fields returned by get_stream match the values passed to create_stream.
• The assertion covers start, end and cliff times and the total amount.
• The suite still passes.

Getting started

Fork this repository, clone your fork, and add this repo as upstream:

git clone https://github.com/<your-username>/tricklepay-contracts.git
cd tricklepay-contracts
git remote add upstream https://github.com/TricklePay/tricklepay-contracts.git

Create a branch for this issue:

git checkout -b test/issue-186

Suggested commit message:

test: assert the stored schedule matches the arguments

Run cargo fmt --check, cargo clippy --all-targets -- -D warnings, and cargo test before opening a pull request and linking this issue.