Implement group cloning for recurring savings circles

[big14way]

Allow admins to clone a completed group's settings to start a new cycle with the same members.

Acceptance Criteria:

• Add clone_group(admin, source_group_id) -> u64 function
• Copy token, contribution_amount, cycle_length, max_members from source
• Optionally auto-invite previous members
• New group starts in Forming status
• Reference source group in metadata

Files: contracts/sorosave/src/group.rs, contracts/sorosave/src/types.rs

[jiarongmai]

I can implement this feature. I have experience with similar tasks and can deliver high-quality code. Ready to start immediately!

[er1c-cartman]

Submitted PR: #143

Summary:

• Added clone_group(admin, source_group_id) -> u64 for completed savings groups.
• Copies group settings and previous members into a new Forming group.
• Records source_group_id metadata and registers cloned membership for previous members.
• Added a regression test proving the clone can start a new cycle.

Validation:

• cargo test --package sorosave -> 10 passed
• cargo fmt --check -> passed
• cargo clippy --package sorosave --all-targets -- -D warnings -> passed
• git diff --check -> passed

No secrets, tokens, or private runtime data are included.

[big14way]

youve been assigned