Restructure into src/ layout under pygui package

Move all application source under src/pygui/ and rewire imports,
build config, and QML module path to match.
- Relocate backend/, serialcomm/, and the ISC QML module into
  src/pygui/; convert main.py into pygui/__main__.py with a main()
  entry point (run via `python -m pygui` or the new `isc` script)
- Rewrite absolute imports: backend.* -> pygui.backend.*,
  serialcomm.* -> pygui.serialcomm.* (source + tests)
- Move app icons (isc.ico/icns) into packaging/
- Update README and ISC.qmlproject to the new paths

src/pygui/backend/csv_file_metadata.py

@@ -0,0 +1,51 @@
+from datetime import datetime
+
+
+# ===== CSV Metadata Model =====
+class CSVFileMetadata:
+    # ===== Lifecycle =====
+    def __init__(self, wafer="", date="", chamber="", notes="", master_type="", filename="", columns=0):
+        self.wafer = wafer
+        self.date = date
+        self.chamber = chamber
+        self.notes = notes
+        self.master_type = master_type
+
+        self.filename = filename
+        self.columns = columns
+
+    # ===== Accessors =====
+    def get_wafer_type(self) -> str:
+        """Return the first character of the wafer string, or empty if none"""
+        return self.wafer[0] if self.wafer else ""
+
+    def get_date(self) -> datetime:
+        """Parsifes the date string. Returns current time if parsing fails"""
+        date_format = "%Y-%m-%d %H:%M:%S"
+        try:
+            return datetime.strptime(self.date, date_format)
+        except (ValueError, TypeError):
+            # If format is wrong or date is None, return current time
+            return datetime.now()
+
+    # ===== Formatting =====
+    @staticmethod
+    def format_date(dt: datetime) -> str:
+        """Formats a datetime object into the standard ISO-like string."""
+        if not isinstance(dt, datetime):
+            return ""
+        return dt.strftime("%Y-%m-%d %H:%M:%S")
+
+    # ===== Serialization =====
+    def to_dict(self) -> dict:
+        return {
+            "wafer": self.wafer,
+            "date": self.string_date_format(),  # Ensure we save as string
+            "chamber": self.chamber,
+            "notes": self.notes,
+            "masterType": self.master_type,
+        }
+
+    def string_date_format(self) -> str:
+        """Helper to ensure the date is always a string for JSON."""
+        return self.format_date(self.get_date())