fix: remove v1 route and update tests for devnet v0.12

[geoxel]

fix: remove v1 route and update tests for devnet v0.12

Drop support for the v1 relayer API route and migrate all routing logic to v2 only, in preparation for devnet v0.12.

Core changes:

• relayerUrl.ts: parseRelayerUrl no longer accepts fallbackVersion or relayerRouteVersion. Always returns version 2. v1 Zama URLs (Sepolia/Mainnet) are automatically upgraded to their v2 equivalents.
• createRelayerProvider.ts: drops defaultRelayerVersion parameter and unconditionally returns a RelayerV2Provider. RelayerV1Provider removed.
• createRelayerFhevm.ts: simplified, v1 provider wiring removed.

Test cleanup:

• Deleted RelayerV1Fhevm.test.ts and RelayerV1Provider.test.ts.
• Pruned index.test.ts, relayerUrl.test.ts, and v2 test files to remove v1 test cases and update URL expectations.
• Added src/test/scripts/test-devnet.sh for devnet integration testing.
• Simplified test-testnet.sh to remove v1-specific test paths.

CLI / bin updates:

• Removed "--version" option from bin/ commands (input-proof.js, public-decrypt.js, user-decrypt.js, etc.) and bin/utils.js.

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[0xalexbel]

LGTM!

[IceTDrinker]

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