feat: Create PDFExporter class for invoice generation

This commit introduces a `PDFExporter` class to handle PDF invoice
generation logic.  This separates PDF creation from the main
application logic, improving modularity.

- Created PDFExporter class with methods for generating PDF invoices.
- Moved PDF generation code from MainWindow to PDFExporter.
- Added attributes for company and client information.

pdf_exporter.py

@@ -0,0 +1,115 @@
+# timelogix/pdf_exporter.py
+import datetime
+from reportlab.lib.pagesizes import letter
+from reportlab.pdfgen import canvas
+from reportlab.lib import colors
+from reportlab.platypus import Table, TableStyle
+from reportlab.lib.styles import getSampleStyleSheet
+from reportlab.lib.units import inch
+
+
+class PDFExporter:
+    def __init__(self):
+        self.company_name = "Your Company Name"
+        self.company_address = "123 Main St, Anytown, USA"
+        self.client_name = "Client Name"
+        self.client_address = "Client Address"
+        self.hourly_rate = 60.00
+        self.invoice_number = 1
+
+    def export_to_pdf(self, log_entries):
+        try:
+            filename = f"invoice_{self.invoice_number}.pdf"
+            c = canvas.Canvas(filename, pagesize=letter)
+            styles = getSampleStyleSheet()
+
+            # --- Header ---
+            c.setFont("Helvetica-Bold", 16)
+            c.drawString(inch, 7.5 * inch, self.company_name)
+            c.setFont("Helvetica", 10)
+            c.drawString(inch, 7.3 * inch, self.company_address)
+
+            c.setFont("Helvetica-Bold", 12)
+            c.drawString(4.5 * inch, 7.5 * inch, "Invoice")
+            c.setFont("Helvetica", 10)
+            c.drawString(
+                4.5 * inch, 7.3 * inch, f"Invoice Number: {self.invoice_number}"
+            )
+            current_date = datetime.datetime.now().strftime("%Y-%m-%d")
+            c.drawString(4.5 * inch, 7.1 * inch, f"Date: {current_date}")
+
+            # --- Client Info ---
+            bill_to_y = 6.5 * inch  # Starting y position for "Bill To:"
+            line_height = 0.2 * inch  # Height for each line of text
+
+            c.setFont("Helvetica-Bold", 12)
+            c.drawString(inch, bill_to_y, "Bill To:")  # "Bill To:" label
+
+            c.setFont("Helvetica", 10)
+            c.drawString(
+                inch, bill_to_y - line_height, self.client_name
+            )  # Client Name
+            c.drawString(
+                inch, bill_to_y - 2 * line_height, self.client_address
+            )  # Client Address
+
+            # --- Table ---
+            data = [["Task", "Project", "Hours", "Rate", "Total"]]
+            total_amount = 0
+
+            for entry in log_entries:
+                hours = entry["duration"] / 3600
+                line_total = hours * self.hourly_rate
+                total_amount += line_total
+                data.append(
+                    [
+                        entry["task"],
+                        entry["project"],
+                        f"{hours:.2f}",
+                        f"${self.hourly_rate:.2f}",
+                        f"${line_total:.2f}",
+                    ]
+                )
+
+            table = Table(data, colWidths=[1.5 * inch, 1.5 * inch, inch, inch, inch])
+            style = TableStyle(
+                [
+                    ("BACKGROUND", (0, 0), (-1, 0), colors.grey),
+                    ("TEXTCOLOR", (0, 0), (-1, 0), colors.whitesmoke),
+                    ("ALIGN", (0, 0), (-1, -1), "CENTER"),
+                    ("FONTNAME", (0, 0), (-1, 0), "Helvetica-Bold"),
+                    ("BOTTOMPADDING", (0, 0), (-1, 0), 12),
+                    ("BACKGROUND", (0, 1), (-1, -1), colors.beige),
+                    ("GRID", (0, 0), (-1, -1), 1, colors.black),
+                ]
+            )
+            table.setStyle(style)
+            table.wrapOn(c, letter[0] - 2 * inch, letter[1] - 2 * inch)
+            table.drawOn(c, inch, 4 * inch)
+
+            # --- Totals ---
+            c.setFont("Helvetica-Bold", 12)
+            c.drawString(4 * inch, 3.5 * inch, "Subtotal:")
+            c.setFont("Helvetica", 12)
+            c.drawRightString(5.5 * inch, 3.5 * inch, f"${total_amount:.2f}")
+
+            c.setFont("Helvetica-Bold", 12)
+            c.drawString(4 * inch, 3.3 * inch, "Tax (0%):")
+            c.setFont("Helvetica", 12)
+            c.drawRightString(5.5 * inch, 3.3 * inch, "$0.00")
+
+            c.setFont("Helvetica-Bold", 12)
+            c.drawString(4 * inch, 3.1 * inch, "Total:")
+            c.setFont("Helvetica", 12)
+            c.drawRightString(5.5 * inch, 3.1 * inch, f"${total_amount:.2f}")
+
+            # --- Notes ---
+            c.setFont("Helvetica", 10)
+            c.drawString(inch, 2 * inch, "Notes:")
+            c.drawString(inch, 1.8 * inch, "Thank you for your business!")
+
+            c.save()
+            print(f"Exported to PDF successfully as {filename}!")
+
+        except Exception as e:
+            print(f"Error exporting to PDF: {e}")