fix: normalize non-OK API responses

[YfengJ]

Summary

Fixes #1.

Normalizes non-2xx HTTP responses in the shared frontend API client into ApiError objects so callers no longer receive 4xx/5xx responses as successful ApiResponse<T> values.

Changes

• Convert non-OK fetch responses into ApiError before the success response-interceptor path.
• Preserve HTTP status, request ID, path, response body details, and actionable suggestions for JSON and text error bodies.
• Keep timeout and network failures on the existing normalizeError path.
• Avoid retrying ordinary 4xx GET responses while keeping retry behavior for transient failures such as timeout, 429, and 5xx.
• Add documented validation notes for 2xx success, 401 JSON, 429, 500 text, aborted request, and network failure cases.
• Include diagnostic/build-b172b833.json from the required python3 build.py run. The encrypted .logd could not be created because the local encryptly preflight fails before module builds.

Testing

• cd frontend && npm ci --ignore-scripts --no-audit --no-fund
• cd frontend && npm run build passes.
• git diff --check passes.
• python3 build.py was run and failed in the required diagnostic preflight because encryptly cannot run in this environment. It generated and committed diagnostic/build-b172b833.json; no .logd was produced.

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

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• I would like to request that my diagnostic build log is removed before merging