fix(kds): prevent setInterval leak during fallback polling

[khaira777]

Summary

Fixes a severe CPU spike (~300%+) and massive context switching in the Electron renderer process caused by an interval leak in the WebSocket fallback logic for the KDS (Kitchen Display System).

Fixes #69

Changes

• Clears restIntervalRef before setting a new interval in startRestPolling
• Reorders hooks to prevent TDZ ReferenceError during initial render
• Adds missing dependencies to useCallback and useEffect arrays
• Simplifies fallback polling in tryWebSocket

Checklist

• Tests added/updated for new functionality
• npm run build passes (no TypeScript errors)
• npm run lint passes
• Database migrations are non-destructive (UPDATE, not DROP)
• Breaking changes documented (if any)
• Related issue linked above

Screenshots

N/A