feat: robust metric extraction with confidence score and proof snippets

- fixed Year-Prefix Bug in MetricParser
- added metric_confidence and metric_proof_text to database
- added Entity-Check and Annual-Priority to LLM prompt
- improved UI: added confidence traffic light and mouse-over proof tooltip
- restored missing API endpoints (create, bulk, wiki-override)

company-explorer/frontend/node_modules/tailwindcss/src/util/isPlainObject.js

@@ -0,0 +1,8 @@
+export default function isPlainObject(value) {
+  if (Object.prototype.toString.call(value) !== '[object Object]') {
+    return false
+  }
+
+  const prototype = Object.getPrototypeOf(value)
+  return prototype === null || Object.getPrototypeOf(prototype) === null
+}