feat: JSON, Excel export and time summary

- #23: add JSONFormatter and XLSXFormatter
- add openpyxl dependency for .xlsx export
- #22: add --summary flag and calculate_summary() in report_builder
- ReportRow now carries raw hours for summary calculations
- update CLI help and README with .json/.xlsx formats and --summary
- add tests for new formatters and summary computation

Closes #22, closes #23

redmine_reporter/formatters/xlsx.py

@@ -0,0 +1,42 @@
+from typing import List
+
+from openpyxl import Workbook
+from openpyxl.styles import Font
+
+from ..types import ReportRow
+from .base import Formatter
+
+
+class XLSXFormatter(Formatter):
+    """Форматтер для экспорта отчёта в Excel (.xlsx)."""
+
+    def __init__(self, **_kwargs):
+        super().__init__()
+
+    def format(self, rows: List[ReportRow]) -> Workbook:
+        wb = Workbook()
+        ws = wb.active
+        ws.title = "Report"
+
+        headers = ["Project", "Version", "Issue ID", "Subject", "Status", "Spent Time"]
+        ws.append(headers)
+        for cell in ws[1]:
+            cell.font = Font(bold=True)
+
+        for r in rows:
+            ws.append(
+                [
+                    r["project"],
+                    r["version"],
+                    r["issue_id"],
+                    r["subject"],
+                    r["status_ru"],
+                    r["time_text"],
+                ]
+            )
+
+        return wb
+
+    def save(self, rows: List[ReportRow], output_path: str) -> None:
+        wb = self.format(rows)
+        wb.save(output_path)