[ObedChibunna]

##SUMMARY
Add loading, error, empty, and success tests for the payment, credits, usage, and wallet error pages. Cover payment creation’s idempotency key and payment status updates via WebSocket with polling fallback. Ensure CI checks pass.

Adds component tests for payment, credits, usage, and wallet error pages, covering loading, error, empty, and success states. Also tests payment idempotency and WebSocket-to-polling fallback so key user flows are covered and CI can catch regressions.

Contracts checklist

Adds component coverage for payment, credits, usage, and wallet error pages, including payment creation idempotency and WebSocket-to-polling fallback. Fixes related test and build failures, and updates the contracts toolchain and lockfile to use stable Rust.
If this PR touches anything under contracts/, confirm it against the
pre-deployment security checklist before
requesting review:

• make audit (CT-72 require_auth() coverage) passes.
• Every amount-handling path uses checked arithmetic (CT-73) — no raw
  +/- on amounts.
• Not applicable — this PR does not touch contracts/.

Test plan

• Frontend lint, typecheck, component coverage (161 passed), production build, and wallet Playwright tests (2 passed).
• Backend lint, build, unit tests (716 passed), dependency hygiene checks, and critical-level npm audit.
• Rust formatting and contract authorization audit passed.

Local verification limits: PostgreSQL-dependent backend E2E/migration checks and Rust Clippy/tests/WASM build could not run in this environment.
CLOSES #1990

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