Implement the canonical `milestonex_campaign.wasm` binary and ship it as the default deployment artifact

[P3az3]

Problem Statement Closely related to Issue 14, this is the contract-side feature work: ensure the canonical campaign/ contract compiles to a milestonex_campaign.wasm artifact, gets wasm-opt -Oz'd, and is the binary that the deploy tooling ships.

Expected Outcome

• Makefile target produces target/wasm32v1-none/release/milestonex_campaign.wasm.
• make optimize runs wasm-opt -Oz and produces a sensible byte-size.
• A regression test asserts the resulting WASM file exists and is < 64 KiB (Soroban ceiling for hosted contracts).

Acceptance Criteria

• Binary exists after make build-wasm.
• Size-cap test passes.
• cargo build does not silently produce only the legacy core binary.

Implementation Notes

• The Makefile already compiles -p milestonex-campaign .... Verify the artifact name.

Affected Files / Modules

• Makefile
• scripts/deploy.sh
• README.md

Dependencies — Issue 14.

[Sammygee12]

Hi, I'd like to work on this issue. I've gone through the description and acceptance criteria and I'm confident I can deliver it. I'll make sure every acceptance criterion is met and submit a clean, tested PR. Please assign it to me.

[grantfox-oss]

🦊 GrantFox — @Sammygee12 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #43)
2. Your PR will be reviewed by the MillestoneX maintainers

Good luck! Track your progress on GrantFox.