Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/lucide-react/dist/esm/context.mjs.map

@@ -0,0 +1 @@
+{"version":3,"file":"context.mjs","sources":["../../src/context.ts"],"sourcesContent":["'use client';\n\nimport { createContext, createElement, type ReactNode, useContext, useMemo } from 'react';\nimport { LucideProps } from './types';\n\ntype LucideConfig = {\n  size: number;\n  color: string;\n  strokeWidth: number;\n  absoluteStrokeWidth: boolean;\n  className: string;\n};\n\nconst LucideContext = createContext<LucideProps>({});\n\ntype LucideProviderProps = {\n  children: ReactNode;\n} & Partial<LucideConfig>;\n\nexport function LucideProvider({\n  children,\n  size,\n  color,\n  strokeWidth,\n  absoluteStrokeWidth,\n  className,\n}: LucideProviderProps) {\n  const value = useMemo(\n    () => ({\n      size,\n      color,\n      strokeWidth,\n      absoluteStrokeWidth,\n      className,\n    }),\n    [size, color, strokeWidth, absoluteStrokeWidth, className],\n  );\n\n  return createElement(LucideContext.Provider, { value }, children);\n}\n\nexport const useLucideContext = () => useContext(LucideContext);\n"],"names":[],"mappings":";;;;;;;;;;;AAaA;AAMO;AAAwB;AAC7B;AACA;AACA;AACA;AACA;AAEF;AACE;AAAc;AACL;AACL;AACA;AACA;AACA;AACA;AACF;AACyD;AAG3D;AACF;AAEO;;"}