Refactor code style and improve documentation

- Standardized string quotes to single quotes across all files.
- Added docstrings to several functions and classes for better clarity.
- Updated mypy configuration in pyproject.toml for enhanced type checking.
- Ignored specific linting rules for test files in ruff configuration.
- Improved error messages in exception handling for better user feedback.
- Cleaned up code formatting and structure for consistency.

tests/test_session.py

@@ -6,17 +6,17 @@ from yt_shorts_downloader.session import validate_session_file
 
 
 def test_validate_session_file_accepts_valid_youtube_session(tmp_path: Path) -> None:
-    session_file = tmp_path / "cookies.txt"
+    session_file = tmp_path / 'cookies.txt'
     session_file.write_text(
-        "\n".join(
+        '\n'.join(
             [
-                "# Netscape HTTP Cookie File",
-                ".youtube.com\tTRUE\t/\tFALSE\t9999999999\tSID\tvalue1",
-                ".youtube.com\tTRUE\t/\tTRUE\t9999999999\tSAPISID\tvalue2",
-                ".youtube.com\tTRUE\t/\tTRUE\t9999999999\tLOGIN_INFO\tvalue3",
+                '# Netscape HTTP Cookie File',
+                '.youtube.com\tTRUE\t/\tFALSE\t9999999999\tSID\tvalue1',
+                '.youtube.com\tTRUE\t/\tTRUE\t9999999999\tSAPISID\tvalue2',
+                '.youtube.com\tTRUE\t/\tTRUE\t9999999999\tLOGIN_INFO\tvalue3',
             ]
         ),
-        encoding="utf-8",
+        encoding='utf-8',
     )
 
     validation = validate_session_file(session_file)
@@ -28,8 +28,8 @@ def test_validate_session_file_accepts_valid_youtube_session(tmp_path: Path) ->
 
 
 def test_validate_session_file_rejects_invalid_format(tmp_path: Path) -> None:
-    session_file = tmp_path / "cookies.txt"
-    session_file.write_text("broken\trow", encoding="utf-8")
+    session_file = tmp_path / 'cookies.txt'
+    session_file.write_text('broken\trow', encoding='utf-8')
 
     validation = validate_session_file(session_file)