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/postcss/lib/terminal-highlight.js

@@ -0,0 +1,70 @@
+'use strict'
+
+let pico = require('picocolors')
+
+let tokenizer = require('./tokenize')
+
+let Input
+
+function registerInput(dependant) {
+  Input = dependant
+}
+
+const HIGHLIGHT_THEME = {
+  ';': pico.yellow,
+  ':': pico.yellow,
+  '(': pico.cyan,
+  ')': pico.cyan,
+  '[': pico.yellow,
+  ']': pico.yellow,
+  '{': pico.yellow,
+  '}': pico.yellow,
+  'at-word': pico.cyan,
+  'brackets': pico.cyan,
+  'call': pico.cyan,
+  'class': pico.yellow,
+  'comment': pico.gray,
+  'hash': pico.magenta,
+  'string': pico.green
+}
+
+function getTokenType([type, value], processor) {
+  if (type === 'word') {
+    if (value[0] === '.') {
+      return 'class'
+    }
+    if (value[0] === '#') {
+      return 'hash'
+    }
+  }
+
+  if (!processor.endOfFile()) {
+    let next = processor.nextToken()
+    processor.back(next)
+    if (next[0] === 'brackets' || next[0] === '(') return 'call'
+  }
+
+  return type
+}
+
+function terminalHighlight(css) {
+  let processor = tokenizer(new Input(css), { ignoreErrors: true })
+  let result = ''
+  while (!processor.endOfFile()) {
+    let token = processor.nextToken()
+    let color = HIGHLIGHT_THEME[getTokenType(token, processor)]
+    if (color) {
+      result += token[1]
+        .split(/\r?\n/)
+        .map(i => color(i))
+        .join('\n')
+    } else {
+      result += token[1]
+    }
+  }
+  return result
+}
+
+terminalHighlight.registerInput = registerInput
+
+module.exports = terminalHighlight