Rename firma to atCompany on server and client

Renames the Zeiterfassung-vs-home flag to a clearer English name
(SQL alias AT_COMPANY, model property AT_COMPANY, JSON atCompany)
in both the server query/model and the client AvailabilityInfo
type and people-tile renderer.

server/src/CPATapi.Server/Repository/ZeitConsensRepository.cs

@@ -12,7 +12,7 @@ internal class ZeitConsensRepository(IConfiguration config) : Repository(config)
           ,bu.LOGGED_IN
           ,us.US_EXTENSION
           ,buLast.LAST_STAMP
-          ,buLast.FIRMA
+          ,buLast.AT_COMPANY
         FROM dbo.MA_DATEN ma
         INNER JOIN projectmanagement.dbo.CP_USER us ON us.US_LOGINNAME = ma.MA_USER_NAME
         OUTER APPLY (
@@ -24,7 +24,7 @@ internal class ZeitConsensRepository(IConfiguration config) : Repository(config)
         OUTER APPLY (
           SELECT TOP 1
              bu.BU_BU AS LAST_STAMP
-            ,CASE WHEN bu.BU_TERM = 'Zeiterfassung' THEN 1 ELSE 0 END AS FIRMA
+            ,CASE WHEN bu.BU_TERM = 'Zeiterfassung' THEN 1 ELSE 0 END AS AT_COMPANY
           FROM dbo.BU bu
           WHERE bu.BU_MA_NR = ma.MA_NR
           ORDER BY bu.BU_BU DESC