chore: record Universal Router 2.1.2 deployment addresses

[dianakocsis]

Records the UniversalRouter#v2.1.2 deployment across the 23 chains that have a deployments file in this repo. The dev portal reads these files, so 2.1.2 is currently missing from it — see this thread.

Purely additive: 46 files, 690 insertions, 0 deletions. Each chain gets a TOC line, a summary-table row, a detail section and a latest JSON entry, matching the existing forge-chronicles shape.

Why there are no broadcast files

2.1.2 was deployed from the universal-router repo rather than through the briefcase here, so there is no broadcast log, task file or submodule bump to accompany it. Addresses, deployment transactions and initcode hashes come from that repo's broadcast output; the initcode hashes were re-derived as keccak(tx.input) and confirmed against the entry already recorded for mainnet.

Verification

Every recorded address was checked per-chain against both the 2.1.2 release notes and universal-router/deploy-addresses/ — 23/23 agree on all three. The .md summary row, .md detail section and .json entry were also checked against each other: 23 chains, 0 mismatches.

Recorded	Ethereum, Optimism, BNB Chain, Unichain, Polygon, Monad, X Layer, Worldchain, Unichain Sepolia, Soneium, Tempo, MegaETH, Robinhood, Arc, Base, Sepolia, Arbitrum, Celo, Avalanche, Ink, Linea, Blast, Zora
Omitted	Base Sepolia (84532), HyperEVM (999) — neither has a deployments file in this repo today

HyperEVM is worth a separate look: its 2.1.2 is live and verified (bytecode identical to Base's 2.1.2 apart from immutables), but it has no entry in universal-router/deploy-addresses/ and no broadcast log, so it reached the release notes through a path neither repo records.

Overlap with #165

#165 also adds 2.1.2 for mainnet, sepolia and ink (6 files). The values here are pinned to be byte-identical to that PR, so the content agrees — but whichever merges second will need a rebase. Mainnet is included here deliberately, since deployments/1.md is the file the dev portal is serving stale.

Notes: commit-hash links point at universal-router (where 802fe4c actually lives) rather than the git@github.com:Uniswap/contracts/... form used by older entries. Timestamps for the 20 chains not shared with #165 come from broadcast run time, so they are within ~30s of block time.

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