refactor: restructure core utilities, typing, and request handling

- In `g4f/__init__.py`, changed logger setup to use fixed "g4f" name and refactored `ChatCompletion.create` and `create_async` to share `_prepare_request` logic for preprocessing arguments
- In `g4f/config.py`, added `__future__.annotations`, `lru_cache` import, wrapped `get_config_dir` with `@lru_cache`, and simplified platform branch logic
- In `g4f/cookies.py`, added typing imports, renamed `browsers` to `BROWSERS`, reformatted `DOMAINS`, updated docstrings, improved loop logic in `load_cookies_from_browsers` with additional exception handling, split HAR/JSON parsing into `_parse_har_file` and `_parse_json_cookie_file`, and enhanced `read_cookie_files` with optional filters and `.env` loading
- In `g4f/debug.py`, added enable/disable logging functions, updated log handler typing, appended messages to `logs` in `log()`, and improved `error()` formatting
- In `g4f/errors.py`, introduced base `G4FError` and updated all exception classes to inherit from it or relevant subclasses, with descriptive docstrings for each
- In `g4f/files.py`, added `max_length` parameter to `secure_filename`, adjusted regex formatting, and added docstring; updated `get_bucket_dir` to sanitize parts inline with docstring
- In `g4f/typing.py`, added `__future__.annotations`, reorganized imports, restricted PIL import to type-checking, defined `ContentPart` and `Message` TypedDicts, updated type aliases and `__all__` to include new types
- In `g4f/version.py`, added `lru_cache` and request timeout constant, applied caching to `get_pypi_version` and `get_github_version`, added response validation and explicit exceptions, refactored `VersionUtils.current_version` with clearer sources and error on miss, changed `check_version` to return a boolean with optional silent mode, and improved error handling outputs

g4f/typing.py

@@ -1,42 +1,89 @@
-import os
-from typing import Any, AsyncGenerator, Generator, AsyncIterator, Iterator, NewType, Tuple, Union, List, Dict, Type, IO, Optional, TypedDict
+from __future__ import annotations
 
-try:
-    from PIL.Image import Image
-except ImportError:
-    class Image:
+import os
+from typing import (
+    Any,
+    AsyncGenerator,
+    Generator,
+    AsyncIterator,
+    Iterator,
+    NewType,
+    Tuple,
+    Union,
+    List,
+    Dict,
+    Type,
+    IO,
+    Optional,
+    TypedDict,
+    TYPE_CHECKING,
+)
+
+# Only import PIL for type-checkers; no runtime dependency required.
+if TYPE_CHECKING:
+    from PIL.Image import Image as PILImage
+else:
+    class PILImage:  # minimal placeholder to avoid runtime import errors
         pass
 
+# Response chunk type from providers
 from .providers.response import ResponseType
 
-SHA256 = NewType('sha_256_hash', str)
+# ---- Hashes & cookie aliases -------------------------------------------------
+
+SHA256 = NewType("SHA256", str)
+Cookies = Dict[str, str]
+
+# ---- Streaming result types --------------------------------------------------
+
 CreateResult = Iterator[Union[str, ResponseType]]
 AsyncResult = AsyncIterator[Union[str, ResponseType]]
-Messages = List[Dict[str, Union[str, List[Dict[str, Union[str, Dict[str, str]]]]]]]
-Cookies = Dict[str, str]
-ImageType = Union[str, bytes, IO, Image, os.PathLike]
+
+# ---- Message schema ----------------------------------------------------------
+# Typical message structure:
+#   {"role": "user" | "assistant" | "system" | "tool", "content": str | [ContentPart, ...]}
+# where content parts can be text or (optionally) structured pieces like images.
+
+class ContentPart(TypedDict, total=False):
+    type: str           # e.g., "text", "image_url", etc.
+    text: str           # present when type == "text"
+    image_url: Dict[str, str]  # present when type == "image_url"
+
+class Message(TypedDict):
+    role: str
+    content: Union[str, List[ContentPart]]
+
+Messages = List[Message]
+
+# ---- Media inputs ------------------------------------------------------------
+
+# Paths, raw bytes, file-like objects, or PIL Image objects are accepted.
+ImageType = Union[str, bytes, IO[bytes], PILImage, os.PathLike]
 MediaListType = List[Tuple[ImageType, Optional[str]]]
 
 __all__ = [
-    'Any',
-    'AsyncGenerator',
-    'Generator',
-    'AsyncIterator',
-    'Iterator'
-    'Tuple',
-    'Union',
-    'List',
-    'Dict',
-    'Type',
-    'IO',
-    'Optional',
-    'TypedDict',
-    'SHA256',
-    'CreateResult',
-    'AsyncResult',
-    'Messages',
-    'Cookies',
-    'Image',
-    'ImageType',
-    'MediaListType'
-]
+    "Any",
+    "AsyncGenerator",
+    "Generator",
+    "AsyncIterator",
+    "Iterator",
+    "Tuple",
+    "Union",
+    "List",
+    "Dict",
+    "Type",
+    "IO",
+    "Optional",
+    "TypedDict",
+    "SHA256",
+    "CreateResult",
+    "AsyncResult",
+    "Messages",
+    "Message",
+    "ContentPart",
+    "Cookies",
+    "Image",
+    "ImageType",
+    "MediaListType",
+    "ResponseType",
+]