[$45 BOUNTY] [TypeScript] Add guarded API token refresh handling

[9904099]

Bounty: $45 (LT)
Area: frontend/src/services/api.ts
Current state: The API client has retry plumbing, but token refresh is still a TODO and concurrent 401 responses can trigger duplicated refresh work or leave callers with inconsistent auth state.
What is needed: Implement a guarded token refresh flow that deduplicates concurrent refresh attempts and retries the original request once after a successful refresh.

Acceptance criteria:

• Add a single-flight refresh guard so multiple simultaneous 401 responses share one refresh operation.
• Retry the original request exactly once after refresh succeeds, preserving method, headers, and body.
• Clear auth state and surface a typed authentication error when refresh fails.
• Avoid retrying unsafe loops when the refresh endpoint itself returns 401/403.
• Add unit coverage or an executable test fixture for concurrent 401s, refresh failure, and successful retry.

Required validation:

• Run python3 build.py
• Include the generated diagnostic .logd artifact from diagnostic/build-XXX.logd in the PR; also include diagnostic/build-XXX.json if present
• Use .github/pull_request_template.md for your submission

[Rachaelisa]

/claim #2

I'm on it. Reading through the project now and will submit a PR shortly.

[Soengkit]

/submit #9

PR: #9

Implemented guarded API token refresh for frontend/src/services/api.ts:

• concurrent 401/403 responses share one refresh operation
• original request is retried once after refresh succeeds
• refresh failure clears local auth state and throws a typed 401
• /auth/refresh 401/403 does not recursively trigger another refresh
• added executable validation fixture and npm run test:api-refresh

Validation:

• cd frontend && npm install passed
• cd frontend && npm run test:api-refresh passed
• cd frontend && npm run build passed
• git diff --check origin/main...HEAD passed
• python3 build.py generated real diagnostic artifacts

Diagnostic artifacts committed in the PR:

• diagnostic/build-ac1a4b1e.logd
• diagnostic/build-ac1a4b1e.json

Build note: repository-wide python3 build.py recorded 8/10 modules passing. The touched frontend module passed; the remaining failures were local environment/toolchain issues in frailbox C compilation on macOS and openapi-haskell missing Data.Yaml.

[xudexing19920829]

I would like to claim this bounty ($45).

My experience:

• TypeScript API development
• Token refresh mechanisms
• Guard clauses and validation

My plan:

1. Fork and study existing code
2. Add guarded API token refresh handler
3. Implement proper validation and error handling
4. Submit PR

I can start immediately.