fix(config): treat a wrongly typed app.json value as invalid instead of converting it

PLAN 4.3 lets a field of the wrong type fall back to its default alone.
Newtonsoft converted such values implicitly, so "delete-card": 0 became
false and "custom-pixels": "500" became 500. Booleans, integers and
strings are now read only from tokens of exactly that type.

YKanBan.Tests/Storage/AppData/AppConfigStoreTests.cs

@@ -222,6 +222,13 @@ public class AppConfigStoreTests
     [DataRow("\"column-width\": { \"custom-pixels\": \"wide\" }")]
     [DataRow("\"confirmations\": { \"delete-card\": \"nope\" }")]
     [DataRow("\"version\": \"one\"")]
+    [DataRow("\"version\": \"1\"")]
+    [DataRow("\"language\": [\"zh-Hans\"]")]
+    [DataRow("\"confirmations\": { \"delete-card\": 0 }")]
+    [DataRow("\"confirmations\": { \"delete-card\": \"false\" }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": \"500\" }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": 500.0 }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": 99999999999 }")]
     public void InvalidFieldFallsBackAloneWithoutBackup(string invalidMember)
     {
         using var directory = new TempDirectory();