Move test runs into the test-run folder, add TimestampStrings, add basic tests via pytest

pytest added for dev.
Move all the test run python scripts into the "test-run" folder, so we can use the tests/ folder for just tests.

Setup one test for the TimestampStrings class with pytests in tests/unit/string_handling/test_timestamp_strings.py

test-run/timestamp_strings/timestamp_strings.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env -S uv run --script
+
+"""
+Test for double byte format
+"""
+
+from corelibs.string_handling.timestamp_strings import TimestampStrings
+
+
+def main():
+    ts = TimestampStrings()
+    print(f"TS: {ts.timestamp_now}")
+
+    try:
+        ts = TimestampStrings("invalid")
+    except ValueError as e:
+        print(f"Value error: {e}")
+
+
+if __name__ == "__main__":
+    main()
+
+# __END__