fix(ui-server): harmonize setSupervisionUrl semantics and text descriptions

fix(ui-server): harmonize setSupervisionUrl semantics and text descriptions

- Fix SetSupervisionUrl.vue passing empty credentials that silently
  clear existing values; align with AddChargingStations.vue pattern
- Fix double saveStationInfo() call and missing updated event when
  only URL changes in ChargingStation.setSupervisionUrl
- Remove verbose JSDoc, redundant comment, and parenthetical UI label
- Harmonize MCP descriptions: use natural language instead of camelCase
  code names, unify credential field descriptions across schemas