feat(#45): emergency pause admin role for BlendLeverageStrategy

[obanai9]

Summary

Implements issue #45 — D4: Emergency pause admin role.

• storage.rs: adds Admin and Paused keys to DataKey; new helpers set_admin, get_admin, set_paused, is_paused.
• lib.rs: ninth constructor arg admin: Address; new public methods pause(), unpause(), paused(), get_admin().
• pause() and unpause() are gated by the admin address set at init and emit an on-chain event (pause, state) → bool.
• deposit() and harvest() return StrategyError::NotAuthorized when paused; withdraw() is unaffected so users can always exit.

Test plan

• Verify BlendLeverageStrategy::pause() blocks deposit() and harvest(); withdraw() succeeds while paused.
• Verify unpause() restores normal operation.
• Confirm PauseStateChange events are emitted on every state transition.
• Confirm non-admin callers are rejected by pause() and unpause().

Closes #45

🤖 Generated with Claude Code

[Dgetsylver]

The core mechanism is sound: pause()/unpause() both resolve the stored admin and call require_auth(), deposits and harvest are gated before any transfer, withdrawals stay open, and is_paused fail-opens to normal for fresh deploys. Two blockers before this can merge:

1. scripts/deploy_strategy.ts is not updated. The constructor now requires a 9th arg (init_args[8] admin, with .expect("Missing: admin")), but the deploy script still builds args [0..7] — every deploy panics. Please update the script in this PR.
2. No tests. The PR's own test plan is unchecked. Minimum set: non-admin pause/unpause rejected; deposit blocked while paused; withdraw succeeds while paused; unpause restores deposit.

Nice-to-haves (not blocking): a dedicated Paused error variant instead of NotAuthorized so callers can distinguish the two; consider an admin-rotation path (admin is currently immutable while keeper has set_keeper).

[Dgetsylver]

Thanks! Heads-up: the admin role landed on main via D3, but pause/unpause is still unique and wanted. Could you rebase the pause logic onto latest main (the constructor signature changed)? (closes #45)