chore: consistency and dead code cleanup

[ValentinVPK]

Description:

Resolve two batches of non-behavioral cleanup across the reference contracts: consistency/dead-code issues (#129) and identifier/doc typos plus one misnamed function (#128). Nothing changes on-chain behavior except the single, isolated send0x1 fix noted below. Delivered as two commits, one per issue.

#129 — consistency & dead code:

• Remove the inaccurate /// @dev This function reverts if the call is not successful comment from the non-reverting info getters in token-service/HederaTokenService.sol and token-service-v2/HederaTokenService.sol (12 each — the wrappers return UNKNOWN, they don't revert)
• Fix HRC1215Contract.sol license UNLICENSED → Apache-2.0
• Raise HederaScheduleService.sol pragma >=0.4.9 → >=0.5.0 (required by its abi.decode usage)
• Make PrngSystemContract inherit its interface (is IPrngSystemContract + override)
• Add payable to Airdrop.multipleNftAirdrop for parity with the other airdrop entrypoints
• Remove the duplicate contract Sample from InternalCallee.sol and import the canonical Sample.sol (artifact-name collision)
• Drop unused imports / inheritance: HederaTokenService from HRC755Contract; ExpiryHelper+KeyHelper from TokenQuery/TokenTransfer/TokenManagement; ExpiryHelper from TokenCreateContract/TokenCreateCustom

#128 — identifier/doc typos + misnamed function:

• Fix enum DELEGETABLE_CONTRACT_ID → DELEGATABLE_CONTRACT_ID in token-service/KeyHelper.sol and token-service-v2/KeyHelper.sol
• Fix EDCSA → ECDSA in account-service/{IHRC632,HederaAccountService,IHederaAccountService}.sol
• Fix tineycents → tinycents in exchange-rate/ExchangeRateMock.sol
• Fix receipient → recipient in token-service/AtomicHTS.sol
• Make EcrecoverCaller.send0x1 actually use .send() (returning the success bool) instead of .transfer(), so it's genuinely distinct from transfer0x1

Related issue(s):

Fixes #129
Fixes #128

Notes for reviewer:

Verified with npx hardhat compile (clean, 64 files, no new warnings). 21 files changed across two commits. The CI lint (eslint . + prettier test) doesn't touch Solidity, so no formatting impact.

Scope / behavior notes worth a look:

• send0x1 is the only behavioral change in either issue. .transfer() reverts on failure; .send() returns a bool and does not revert. The function now returns that bool and deliberately does not revert() on failure (that non-reverting behavior is the point of .send vs .transfer). It has no callers/tests in the repo, so nothing depends on the old behavior.
• Enum rename is a source-level breaking change. DELEGETABLE_CONTRACT_ID → DELEGATABLE_CONTRACT_ID does not change the enum's on-wire integer value, but downstream code referencing the old (misspelled) name will no longer compile.
• Consistency issues and dead/duplicate code across several contracts #129 Item C narrowed to Prng only. The issue also listed ExchangeRateSystemContract/ExchangeRateMock and HederaAccountService, but those can't inherit their imported interface: it's the precompile's ABI (used only for .selector), and their wrappers are internal while the interface functions are external — an internal function can't satisfy an external interface, so it wouldn't compile and is semantically backwards (they're consumers, not implementations). Only PrngSystemContract is a genuine implementer.
• Consistency issues and dead/duplicate code across several contracts #129 Item F broadened; AtomicHTS pragma dropped. TokenCreateContract/TokenCreateCustom also carried dead ExpiryHelper inheritance (they use KeyHelper, never ExpiryHelper), so those were included. ExpiryHelper.sol now has no importers but is intentionally kept — it's a published helper (part of the ExpiryHelper/FeeHelper/KeyHelper set), so deleting it would be a breaking change to the published surface. The issue's proposed AtomicHTS pragma change was dropped: there's no single project-wide pragma rule (>=0.5.0 <0.9.0 and >=0.4.9 <0.9.0 are tied within token-service/), so it would have been arbitrary rather than an alignment.

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