Implement contract pause mechanism (global)

[big14way]

Add a global pause/unpause for the entire protocol (not just individual groups).

Acceptance Criteria:

• Add paused flag to instance storage
• Check flag in all state-changing functions
• Only protocol admin can pause/unpause
• Emit pause events

Files: contracts/sorosave/src/lib.rs, contracts/sorosave/src/storage.rs

[WuXieSec]

/attempt #42

I can implement a global pause mechanism with tests quickly.

Plan:

1. Add pause/unpause admin controls
2. Enforce pause checks on mutating user/admin flows
3. Add tests for blocked actions during pause + resumed behavior after unpause
4. Validate with "cargo test --package sorosave" in ephemeral Rust env, then submit PR

Payout preference: PayPal (wuxiesec@gmail.com) after merge verification.

[WuXieSec]

Update: withdrawing my attempt on this issue for now. Please feel free to reassign/open to other contributors.

[Scottcjn]

Implemented in PR #85: #85

This adds:

• protocol-wide pause state in instance storage
• admin-only pause_protocol / unpause_protocol
• gating on all mutating contract entrypoints while paused
• tests covering admin-only control, blocked mutations, and resumed behavior after unpause

Verified locally with cargo test.