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/postcss/lib/symbols.js

@@ -0,0 +1,5 @@
+'use strict'
+
+module.exports.isClean = Symbol('isClean')
+
+module.exports.my = Symbol('my')