Remove dead code — unused functions, enums, and constants

[DeFiVC]

What

Several functions, types, and constants are defined but never referenced anywhere in the codebase.

Why

Dead code increases maintenance burden, confuses contributors, and may mask incomplete implementations. Removing it keeps the codebase clean and makes the actual API surface clear.

Scope

Remove the following:

1. get_progress_client helper function in learn-token — never called
2. EnrollmentStatus enum in packages/shared/src/constants.rs — never used
3. TOKEN_DECIMALS constant in packages/shared/src/constants.rs — never imported or used

Technical Context

• File: contracts/learn-token/src/lib.rs (lines ~587-590) — get_progress_client
• File: packages/shared/src/constants.rs (lines ~55-62) — EnrollmentStatus, TOKEN_DECIMALS
• claim_reward uses env.invoke_contract directly instead of get_progress_client

Acceptance Criteria

• All three items removed
• cargo check passes with no errors
• cargo test passes — no tests depend on removed code
• No new warnings introduced

[EstherIkechukwu]

I have gone through the description expect a pr in less than 12hrs

[odiliflash-ops]

I would love to work on this issue