Protocal initalization

[Nanafancy]

Here's a summary of all changes made to address issue closes #127 :

Changes Summary
Shared Module (shared/src/)
errors.rs: Removed 3 unused error variants (InvalidAsset, ZeroShares, InvalidReserveFactor) to stay within Soroban's 50-variant #[contracterror] limit. Added 3 new governance error variants: AdminTransferPending, NoAdminTransferPending, CannotTransferToSelf.
events.rs: Added 3 new governance event types with topic methods: ContractInitialized, AdminTransferPending, AdminTransferred. Also added a topic method for the existing RewardsPoolFunded event.
Vault Contract (vault/src/)
state.rs: Added PendingAdmin variant to VaultKey enum.
lib.rs:
initialize() now requires an admin parameter and calls admin.require_auth(). Returns Result<(), Error> instead of panicking.
Added get_admin(), transfer_admin(), accept_admin() for two-step admin rotation.
Added ContractInitialized event emission on init.
Lending Contract (lending/src/lib.rs)
Added ContractAdmin and PendingAdmin variants to PoolKey enum.
Added initialize() function (one-time, requires admin auth).
Added get_contract_admin(), transfer_admin(), accept_admin() for two-step admin rotation.
create_pool() now requires contract admin authorization.
grant_admin() now requires contract admin authorization.
set_rate_limit() now requires contract admin authorization.
Borrowing Contract (borrowing/src/lib.rs)
Added ContractAdmin and PendingAdmin variants to BorrowingKey enum.
initialize() now requires an admin parameter and calls admin.require_auth().
Added get_contract_admin(), transfer_admin(), accept_admin() for two-step admin rotation.
configure_collateral() now requires contract admin authorization.
Rewards Contract (rewards/src/lib.rs)
Added PendingAdmin variant to RewardsKey enum.
initialize() now returns Result<(), Error>, requires admin.require_auth(), and emits ContractInitialized.
initialize_rewards() now returns Result<(), Error>, requires admin.require_auth(), prevents double-init, and emits ContractInitialized.
grant_admin() now requires current admin authorization.
fund_rewards_pool() now requires admin authorization via pool.admin.require_auth().
add_milestone() now requires admin authorization.
Added transfer_admin() and accept_admin() for two-step admin rotation.
Deployment Script (scripts/initialize.sh)
Requires ADMIN environment variable for all contracts.
Added per-contract admin variables (STREAKS_ADMIN, LENDING_ADMIN, etc.).
All initialization calls now pass --admin parameter.
Improved error messages and validation.
Post-initialization summary prints all admin addresses.
Tests
vault/tests/test_vault_governance.rs (new): 13 tests covering initialization, double-init prevention, admin auth for config, two-step admin transfer, unauthorized access prevention, and backward-compatible vault operations.
rewards/tests/test_rewards_governance.rs (new): 12 tests covering initialization, double-init prevention, admin auth for grant_admin/fund/add_milestone, two-step admin transfer, and full reward flow.
rewards/tests/test_rewards.rs (updated): Added mock_all_auths() to all tests to support new require_auth() calls.
vault/tests/progression_integration.rs (updated): Added mock_all_auths() and updated vault.initialize() call to include admin parameter.

[Nanafancy]

@Nabeelahh pr sent please review