scholarship_treasury: submit_proposal hardcodes exactly 3 milestones

[Anuoluwapo25]

Bug

submit_proposal validates that both milestone_titles and milestone_dates have exactly 3 entries, but the Proposal struct stores them as Vec<String> with no inherent length limit, and no other contract logic enforces 3 milestones anywhere else.

File: contracts/scholarship_treasury/src/lib.rs

if amount <= 0 || milestone_titles.len() != 3 || milestone_dates.len() != 3 {
    panic_with_error!(&env, Error::InvalidAmount);  // ← wrong error too
}

Issues:

1. The magic number 3 is undocumented and not configurable.
2. The error used (InvalidAmount) is misleading — this is a validation failure on milestone count, not on amount.
3. Milestone count should be a configurable parameter (e.g., stored at init time) rather than a compile-time constant.

Fix

• Add a milestone_count config stored at initialize time (defaulting to 3 for backwards compatibility).
• Add an InvalidMilestoneCount error variant.
• Validate milestone_titles.len() == configured_milestone_count.