Merge pull request #204 from oasisprotocol/matevz/feature/solidity-version-upgradeable

solidity: VERSION, cleanups, Safe deployment tooling, Sourcify verification, other hardhat tooling

Author: matevz

.gitignore

@@ -88,6 +88,8 @@ accounting-module
 # Local auth-token store (SQLite via diskcache) — never commit
 .auth_tokens/
 
-# OpenZeppelin upgrades manifests generated by local runs; remove this if you
-# decide to track production upgrade manifests deliberately
-.openzeppelin/
+# OpenZeppelin upgrades manifests: ignore sapphire-localnet (chain 23293)
+# manifests. Production sapphire/sapphire-testnet manifests (23294/23295) are
+# tracked in git so `hardhat upgrade`'s validateUpgrade() has a real
+# storage layout to check against.
+solidity/.openzeppelin/unknown-23293.json