docs: add crate metadata to all Cargo.toml files (#91)

[Peolite001]

Summary

Adds standardized crate metadata to all Cargo.toml files to prepare the project for potential crates.io publishing. Uses Cargo workspace inheritance to share common fields across the workspace members.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 📝 Documentation update
• 🔧 Smart contract improvement
• 🧪 Test coverage improvement
• 🏗️ CI/Build improvement

Related Issue

Closes #91

Changes Made

-Added [workspace.package] section to root Cargo.toml with shared metadata fields (license, repository, authors, categories, keywords, rust-version)
-Updated contracts/admin/Cargo.toml to inherit workspace metadata and add crate-specific description
-Updated contracts/lifecycle/Cargo.toml to inherit workspace metadata and add crate-specific description
-Updated contracts/token/Cargo.toml to use workspace inheritance instead of hardcoded values
-Added readme = "../../README.md" pointer to all contract crates
-Retained publish = false on all crates to prevent accidental publishing until ready

Testing

How has this been tested?

• Rust unit tests pass (cargo test)
• SDK compiles (npm run build in sdk/)
• Manual testing against Soroban testnet
• New tests added for changes

Test commands run:

# Verify workspace compiles with new metadata
cargo check

# Contract tests
cargo test

## Checklist

- [x] My code follows the project's style guidelines
- [ ] I have added NatSpec-style comments to new Rust functions
- [ ] I have added JSDoc comments to new TypeScript functions
- [ ] I have updated the README if needed
- [ ] My branch follows the naming convention: `feature/<issue-number>-<description>`
- [ ] I have not modified files outside the scope of this issue

## Drips.network Contributor Info

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- **Drips Profile**: [https://www.drips.network/wave/users/fb91e94e-2870-4c67-ba63-fe61d40229d6]
- **Issue Claimed**: #91

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