Backend fix:
- Added presence check in UpdateEmailConfig to detect when rateLimit is
omitted from JSON (vs explicitly set to 0)
- Preserves existing rateLimit value when field is not present in request
- Added comprehensive integration tests covering all scenarios
Frontend fix:
- Added rateLimit to EmailConfig interface
- Fixed getEmailConfig to read rateLimit from server response
- Fixed updateEmailConfig to include rateLimit when set
- Fixed two places in Alerts.tsx that hardcoded rateLimit: 60
Additional fixes:
- Added Array.isArray guards in DiagnosticsPanel sanitization
- Initialized Nodes/PBS arrays in diagnostics response to prevent null
Closes rate limit persistence bug where updating email settings would
reset the rate limit to default value.
b6e4c20e6b