feat: filename template expansion with {date} placeholder

- Add expand_filename_template() to yaml_config.py
- Supports {author}, {from}, {to}, {date}, {ext} placeholders
- {date} formats as DD_MM_YYYY (e.g. 31_03_2026)
- Spaces in author replaced with underscores for safe filenames
- Unknown placeholders left as-is
- Add comprehensive CONFIG.md documentation covering YAML setup, migration, and template syntax

tests/test_config.py

@@ -5,7 +5,7 @@ from unittest import mock
 
 import pytest
 
-from redmine_reporter.config import AppConfig, Config, DEFAULT_REDMINE_VERIFY
+from redmine_reporter.config import DEFAULT_REDMINE_VERIFY, AppConfig, Config
 
 
 @mock.patch.dict(

tests/test_yaml_config.py

@@ -4,10 +4,10 @@ import tempfile
 from pathlib import Path
 from unittest import mock
 
-
 from redmine_reporter.yaml_config import (
     check_file_permissions,
     ensure_config_dir,
+    expand_filename_template,
     resolve_env_vars,
 )
 
@@ -78,3 +78,47 @@ class TestCheckFilePermissions:
             f.chmod(0o600)
             warnings = check_file_permissions(f)
             assert warnings == []
+
+
+class TestExpandFilenameTemplate:
+    """Tests for filename template expansion."""
+
+    def test_expands_all_placeholders(self):
+        result = expand_filename_template(
+            "report_{author}_{from}_{to}.{ext}",
+            author="Кокос А.А.",
+            from_date="2026-06-01",
+            to_date="2026-06-30",
+            ext="xlsx",
+        )
+        assert result == "report_Кокос_А.А._2026-06-01_2026-06-30.xlsx"
+
+    def test_date_placeholder_dd_mm_yyyy(self):
+        result = expand_filename_template(
+            "отчёт_{date}.{ext}",
+            author="Кокос А.А.",
+            from_date="2026-03-01",
+            to_date="2026-03-31",
+            ext="odt",
+        )
+        assert result == "отчёт_31_03_2026.odt"
+
+    def test_no_placeholders_returns_unchanged(self):
+        result = expand_filename_template(
+            "report.odt",
+            author="Кокос А.А.",
+            from_date="2026-01-01",
+            to_date="2026-01-31",
+            ext="odt",
+        )
+        assert result == "report.odt"
+
+    def test_unknown_placeholder_left_as_is(self):
+        result = expand_filename_template(
+            "{author}_{unknown}.{ext}",
+            author="Кокос А.А.",
+            from_date="2026-01-01",
+            to_date="2026-01-31",
+            ext="xlsx",
+        )
+        assert result == "Кокос_А.А._{unknown}.xlsx"