feat(formulus): Add auto-login on 401 errors during sync operations

[Mishael-2584]

Description

Implements automatic re-authentication when 401 Unauthorized errors occur during sync operations (both data sync and app bundle updates), improving UX by preventing manual re-login.

Problem:
When users return to Formulus and attempt to sync after their auth token has expired, they encounter a 401 error and must manually navigate to Settings to re-login before syncing again.

Solution:

• Automatically detects 401 Unauthorized errors during sync operations
• Attempts to re-login using stored credentials from Keychain
• Retries the failed operation once after successful auto-login
• Prevents infinite retry loops (max 1 retry per operation)

Type of Change

• Bug Fix
• New Feature / Enhancement
• Refactor / Code Cleanup
• Documentation Update
• Maintenance / Chore
• Other (please specify):

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Component(s) Affected

• formulus (React Native mobile app)
• formulus-formplayer (React web app)
• synkronus (Go backend server)
• synkronus-cli (Command-line utility)
• Documentation
• DevOps / CI/CD
• Other:

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Related Issue(s)

** Closes #143

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Changes Made

Core Implementation

1. src/api/synkronus/Auth.ts

   • Added autoLogin() function to re-authenticate using stored credentials
   • Added isUnauthorizedError() function to detect various 401 error formats

2. src/api/synkronus/index.ts

   • Updated clearTokenCache() to also clear API instance and config
   • Ensures fresh API instance is created with new token after auto-login

3. src/services/SyncService.ts

   • Added withAutoLoginRetry() wrapper method for automatic retry logic
   • Applied to: syncObservations(), updateAppBundle(), checkForUpdates()
   • Made notification service non-blocking to prevent sync hanging

4. src/screens/SettingsScreen.tsx

   • Ensures server URL is saved before login (required by getApi())
   • Fixed for both manual login and QR code login paths

5. src/screens/SyncScreen.tsx

   • Added timeout protection (30 minutes) to prevent infinite hanging
   • Enhanced error handling for update functions
   • Guaranteed finishSync() is always called in finally block

Test Coverage

6. src/api/synkronus/__tests__/Auth.test.ts (15 tests)

   • Unit tests for isUnauthorizedError() and autoLogin()
   • Covers various 401 error formats and auto-login scenarios

7. src/services/__tests__/SyncService.autoLogin.test.ts (8 tests)

   • Integration tests for auto-login retry logic in sync operations
   • Covers success, failure, and edge cases

Bug Fixes Included

• Sync Hanging Issue: Fixed issue where sync would hang indefinitely after auto-login:
  • Made notification service non-blocking (fire-and-forget pattern)
  • Added 30-minute timeout protection
  • Enhanced error handling for update functions
  • Guaranteed UI state update in finally block

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Testing

• Unit tests added/updated
• Integration tests added/updated
• Manually tested
• Tested on multiple platforms (if applicable)
• Not applicable

Test Results

• ✅ All 23 tests passing
• Run: npm test -- Auth.test.ts SyncService.autoLogin.test.ts

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Breaking Changes

• This PR introduces breaking changes
• This PR does NOT introduce breaking changes

If breaking changes, please describe migration steps:

N/A - This is a backward-compatible enhancement.

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Edge Cases Handled

• ✅ Missing credentials → Shows appropriate error message
• ✅ Invalid credentials → Shows error, doesn't retry
• ✅ Network errors → Passes through without retry
• ✅ Notification service failures → Doesn't block sync
• ✅ Infinite retry prevention → Max 1 retry per operation
• ✅ Timeout protection → 30-minute max sync time

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Documentation Updates

• Documentation has been updated
• Documentation update is not required

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Checklist

• Code follows project style guidelines
• All existing tests pass
• New tests added for new functionality
• PR title follows Conventional Commits format
• Prettier formatting applied
• No linter errors
• Comprehensive error handling
• Detailed logging for debugging

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[r0ssing]

Looks great - thanks @Mishael-2584 ! 🚀
Let's pull a fresh Formulus release once this is merged