fix: record maker-checker task rejections

[LE0-Lin]

What and why

Rejecting a maker-checker task used the DELETE endpoint, removing the audit entry instead of recording the rejection. This change sends the supported reject command through the maker-checker POST endpoint so the decision remains in the audit trail.

It also replaces the browser-native confirmation and hardcoded reject messages with the standard translated destructive dialog, and adds regression coverage that explicitly proves the DELETE endpoint is never called.

Closes #280

Verification

• npm run test:unit — 47 files, 364 tests passed
• npm test -- --watch=false — 868 tests passed
• npm run lint:prune
• npm run build
• npm run i18n:check
• npm run check:icons
• npm run check:test-runner
• Changed files pass Prettier and git diff --check
• UI behavior exercised with adapter-backed component tests; no real Fineract backend was required

Screenshots

Not applicable — this changes confirmation behavior and API semantics without changing layout.

Checklist

• I did not hand-edit generated files under src/app/api/.
• New component or service code uses the adapter boundary in src/app/core/adapters/ instead of direct browser globals or imperative third-party APIs.
• User-facing strings use translation keys.
• I added or updated tests appropriate to this change, or explained why tests were not needed.
• UI workflow changes include suitable e2e coverage, including real-backend testing where relevant. Not added: the API contract and confirm/cancel behavior are covered by component tests; no new route or backend workflow was introduced.
• Commits are signed — see Commit Signing in CONTRIBUTING.md.