fix(hello-world): repair contract lib build after merged refactor (#884)

[kaluuba-org]

Closes #720 #712

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Summary

Upstream main (3b731f2, #884) left the hello-world contract library with 93 compile errors. This PR repairs the crate so cargo check -p hello-world passes cleanly.

What was broken and fixed

• risk_params.rs — the merge mangled get_legacy_risk_params (body truncated mid-expression, leaving an unclosed delimiter) and left a duplicate get_risk_params definition. Restored the legacy getter body and removed the duplicate.
• lib.rs — restored the dropped pub mod timelock; declaration (the crate routes timelock::* entrypoints at lib.rs:2452-2513, so the module was required); typed flags as u32; fixed gov_get_multisig_config return type; fixed the cross-asset and oracle entrypoint result mapping.
• SDK 27 API drift — env.ledger().sequence_number() → .sequence() (flash_loan.rs); ReentrancyGuard::new_with_key(env, key, false); Address::zero() → XDR-constructed zero-contract-address check (private in SDK 27); Vec::remove now takes u32; iter().position closure pattern.
• Enum/structural mismatches — added Paused/Emergency to CircuitBreakerStatus with exhaustive match arms; EmergencyTrigger::AdminEmergency → Admin; abnormal_utilization_threshold_bps → abnormal_utilization_bps; completed CircuitBreakerState construction with tier/affected_pool/guardian_multisig/governance_vote_required; added RecoveryRequest.ready_at.
• Error types — added missing GovernanceError variants (RecoveryNotReady, InvalidActionTypeDelay, EmergencyOverrideAlreadyApproved, InsufficientEmergencyApprovals), missing DebtTokenError conversion arms, and the missing From<EmergencyWithdrawalError> for LendingError.
• Events — added to_shared_proposal_type / to_shared_vote_type / to_shared_emergency_trigger conversions for the shared-events schema.
• Misc — missing Vec imports, borrow-after-move fix in mev_protection.rs, get_static_reserve_factor → get_legacy_reserve_factor, reserve::get_reserve_balance → treasury::get_reserve_balance, and a type annotation in reputation.rs.

Verification

stellar-lend $ cargo check -p hello-world
warning: `hello-world` (lib) generated 26 warnings   # pre-existing, not new
Finished `dev` profile ... in 0.16s

Known remaining breakage (pre-existing, out of scope)

Chronicled for follow-up PRs; none are caused by this change:

1. Test suite does not compile — cargo test -p hello-world fails with ~647 errors across 52 stale test files. The tests target the pre-refactor contract API (e.g. client.get_utilization(), is_operation_paused, get_risk_config) which no longer exists on HelloContractClient. Porting them to the new API is a separate, sizable effort.
2. WASM link fails — stellarlend-common ships a full #[contract] UpgradeManager whose no_mangle exports collide when stellarlend-amm (a hello-world dependency) re-exports those methods: rust-lld: error: duplicate symbol: upgrade_rollback (etc.). Needs stellarlend-common's contract to be feature-gated or split out.
3. Rust toolchain — the release wasm build requires stellar contract build (stellar-cli v25.2+) or the wasm32v1-none target; plain cargo build --target wasm32-unknown-unknown is unsupported by the Soroban Environment.

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