Add CSV format support

Closes #5

redmine_reporter/formatter_csv.py

@@ -0,0 +1,40 @@
+import csv
+import io
+from typing import List, Tuple
+from redminelib.resources import Issue
+from .formatter import get_version, hours_to_human, STATUS_TRANSLATION
+
+
+def format_csv(
+    issue_hours: List[Tuple[Issue, float]],
+    fill_time: bool = True,
+    dialect: str = "excel"
+) -> str:
+    """
+    Formats the list of issues with spent time into CSV.
+    Returns a string containing the CSV content.
+    """
+
+    output = io.StringIO()
+    writer = csv.writer(output, dialect=dialect)
+
+    # Header
+    writer.writerow(["Project", "Version", "Issue ID", "Subject", "Status", "Spent Time"])
+
+    for issue, hours in issue_hours:
+        project = str(issue.project)
+        version = get_version(issue)
+        status_en = str(issue.status)
+        status_ru = STATUS_TRANSLATION.get(status_en, status_en)
+        time_text = hours_to_human(hours) if fill_time else ""
+
+        writer.writerow([
+            project,
+            version,
+            issue.id,
+            issue.subject,
+            status_ru,
+            time_text
+        ])
+
+    return output.getvalue()