Fix CI typecheck blindspot

[Peolite001]

Closes #425

Description

This PR introduces a dedicated type-checking gate (tsc --noEmit) to our CI pipeline and resolves 9 previously undetected type errors in our test files.

Previously, CI relied on next build for type-checking, which only covers modules reachable from the application's build graph, creating a blind spot where test files were silently failing type checks.

Changes included:

• Added typecheck script: Introduced "typecheck": "tsc --noEmit" to package.json.
• Updated CI pipeline: Added a standalone "Typecheck" step to .github/workflows/ci.yml before the build step.
• Fixed type errors in test files:
  • MetricsBar.test.tsx: Added missing reload, mutate, and pendingSettlements properties to the mocked useAsync return values.
  • SettlementTable.test.tsx: Fixed DOM element typecasting by asserting queried nodes as HTMLElement so that @testing-library's within function compiles correctly.

We adopted a "fix-then-gate" approach since there were only 9 errors across 2 files, allowing us to lock down the test file contracts immediately without needing exceptions or tsconfig exclusions.

Checklist

• I added a CHANGELOG.md entry under the next ## [x.y.z] section
  (see the Format note at the top of CHANGELOG.md), or this PR
  is docs-only / test-only / internal tooling and doesn't change
  user-facing behavior. (Note: This PR is test/tooling-only).
• Tests added/updated for the change.