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/bigSign.js

@@ -0,0 +1,3 @@
+export default function bigSign(bigIntValue) {
+  return (bigIntValue > 0n) - (bigIntValue < 0n)
+}