feat(logging): Configure Serilog SQLite sink + UI

appsettings.json:
- Add Application:LogDirectory configuration
- Add Serilog WriteTo.SQLite sink (logs.db in LogDirectory)
- Logs table with UTC timestamps

Program.cs:
- Add Serilog.UI usings
- Configure Serilog.UI with SQLite provider
- Mount UI at /serilog-ui endpoint

Web-based log viewer accessible at: https://localhost:7186/serilog-ui

DocumentOperator.API/appsettings.json

@@ -7,6 +7,10 @@
   },
   "AllowedHosts": "*",
 
+  "Application": {
+    "LogDirectory": "E:\\LogFiles\\Digital Data\\DocumentOperator.API"
+  },
+
   "Serilog": {
     "MinimumLevel": {
       "Default": "Information",
@@ -30,6 +34,14 @@
           "rollingInterval": "Day",
           "outputTemplate": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj} {Properties:j}{NewLine}{Exception}"
         }
+      },
+      {
+        "Name": "SQLite",
+        "Args": {
+          "sqliteDbPath": "E:\\LogFiles\\Digital Data\\DocumentOperator.API\\logs.db",
+          "tableName": "Logs",
+          "storeTimestampInUtc": true
+        }
       }
     ],
     "Enrich": [ "FromLogContext", "WithMachineName", "WithThreadId" ]