chore: add code complexity checks to CI

[GitGuru7]

Makes the TypeScript complexity gates stricter and adds a local formatting helper.

What changed

• Bumped ESLint 7 → 8 (^8.25.0), plus eslint-plugin-promise → ^6.1.1 whose peer range was ESLint 7 only. This is a prerequisite: eslint-plugin-sonarjs@1.0.4 cannot run on ESLint 7.
• ESLint: complexity and sonarjs/cognitive-complexity now error at 15
• Added eslint-plugin-sonarjs (^1.0.4)
• Added a prettier:cached script for local use — CI's prettier:check is unchanged

.solhint.json was left alone — code-complexity is already 15.

Suppressed

One test helper, left with an ignore comment:

• deployVTokenDependencies in tests/hardhat/util/TokenTestHelpers.ts — complexity 21, cognitive complexity 20

Refactored

• deploy/009-deploy-vtokens.ts — the three-way interest-rate-model chain moved into deployInterestRateModel, and the ProtocolShareReserve try/catch into resolveProtocolShareReserve. Order of operations, arguments and throws are unchanged.
• getConfig in helpers/deploymentConfig.ts (complexity 19) — an 18-case switch became a keyed lookup.

Verified

The ESLint 8 bump produced no new findings on its own — same warning count as before. yarn lint:ts and yarn lint:sol both pass with no errors.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with the deployment refactors preserving existing behavior and the updated lint dependencies remaining compatible.

Summary

This PR introduces TypeScript complexity gates, updates the ESLint toolchain required by SonarJS, adds a cached local formatting command, and refactors deployment/configuration code to satisfy the new limits.

• Enforces cyclomatic and cognitive complexity limits of 15.
• Preserves existing VToken interest-model and ProtocolShareReserve deployment behavior through helper extraction.
• Replaces the network configuration switch with an equivalent keyed lookup and retains the development alias.
• Adds a targeted suppression for a pre-existing complex test helper.

_{Reviews (1) · Last reviewed commit: "refactor: replace getConfig network swit..."}

[github-actions]

Package	Line Rate	Branch Rate	Health
contracts	83%	72%	✔
contracts.Gateway	98%	68%	✔
contracts.Gateway.Interfaces	100%	100%	✔
contracts.Lens	95%	69%	✔
contracts.Lens.legacy	0%	0%	❌
contracts.Pool	100%	92%	✔
contracts.Rewards	96%	70%	✔
contracts.Shortfall	100%	85%	✔
contracts.legacy.RiskFund	0%	0%	❌
contracts.lib	100%	89%	✔
Summary	72% (1569 / 2190)	63% (520 / 828)	➖