Add lastStamp to availability and show it on people tiles

Server query extended with MAX(BU_BU) per user as LAST_STAMP,
exposed via the Availability model. Client formats it as
DD.MM. HH:mm next to the loggedIn dot, replacing the mocked time.

server/src/CPATapi.Server/Models/Availability.cs

@@ -11,4 +11,6 @@ public class Availability
     public bool LOGGED_IN { get; set; }
     [JsonPropertyName("extension")]
     public string? US_EXTENSION { get; set; }
+    [JsonPropertyName("lastStamp")]
+    public DateTime? LAST_STAMP { get; set; }
 }

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

@@ -11,6 +11,7 @@ internal class ZeitConsensRepository(IConfiguration config) : Repository(config)
            ma.MA_USER_NAME
           ,bu.LOGGED_IN
           ,us.US_EXTENSION
+          ,buLastStamp.LAST_STAMP
         FROM dbo.MA_DATEN ma
         INNER JOIN projectmanagement.dbo.CP_USER us on us.US_LOGINNAME = ma.MA_USER_NAME
         OUTER APPLY (
@@ -20,6 +21,11 @@ internal class ZeitConsensRepository(IConfiguration config) : Repository(config)
           AND
           BU_BU >= @from AND BU_BU < @to
         ) bu
+        OUTER APPLY (
+          SELECT MAX(BU_BU) AS LAST_STAMP
+          FROM dbo.BU
+          WHERE bu.BU_MA_NR = ma.MA_NR
+        ) buLastStamp
         WHERE
           ma.MA_USER_AKTIV = 1
         """;