feat: add EdgeTTS audio provider and global image→media refactor

- **Docs**
  - `docs/file.md`: update upload instructions to use inline `bucket` content parts instead of `tool_calls/bucket_tool`.
  - `docs/media.md`: add asynchronous audio transcription example, detailed explanation, and notes.

- **New audio provider**
  - Add `g4f/Provider/audio/EdgeTTS.py` implementing Edge Text‑to‑Speech (`EdgeTTS`).
  - Create `g4f/Provider/audio/__init__.py` for provider export.
  - Register provider in `g4f/Provider/__init__.py`.

- **Refactor image → media**
  - Introduce `generated_media/` directory and `get_media_dir()` helper in `g4f/image/copy_images.py`; add `ensure_media_dir()`; keep back‑compat with legacy `generated_images/`.
  - Replace `images_dir` references with `get_media_dir()` across:
    - `g4f/api/__init__.py`
    - `g4f/client/stubs.py`
    - `g4f/gui/server/api.py`
    - `g4f/gui/server/backend_api.py`
    - `g4f/image/copy_images.py`
  - Rename CLI/API config field/flag from `image_provider` to `media_provider` (`g4f/cli.py`, `g4f/api/__init__.py`, `g4f/client/__init__.py`).
  - Extend `g4f/image/__init__.py`
    - add `MEDIA_TYPE_MAP`, `get_extension()`
    - revise `is_allowed_extension()`, `to_input_audio()` to support wider media types.

- **Provider adjustments**
  - `g4f/Provider/ARTA.py`: swap `raise_error()` parameter order.
  - `g4f/Provider/Cloudflare.py`: drop unused `MissingRequirementsError` import; move `get_args_from_nodriver()` inside try; handle `FileNotFoundError`.

- **Core enhancements**
  - `g4f/providers/any_provider.py`: use `default_model` instead of literal `"default"`; broaden model/provider matching; update model list cleanup.
  - `g4f/models.py`: safeguard provider count logic when model name is falsy.
  - `g4f/providers/base_provider.py`: catch `json.JSONDecodeError` when reading auth cache, delete corrupted file.
  - `g4f/providers/response.py`: allow `AudioResponse` to accept extra kwargs.

- **Misc**
  - Remove obsolete `g4f/image.py`.
  - `g4f/Provider/Cloudflare.py`, `g4f/client/types.py`: minor whitespace and import tidy‑ups.

g4f/gui/server/backend_api.py

@@ -25,7 +25,7 @@ from ...tools.run_tools import iter_run_tools
 from ...errors import ProviderNotFoundError
 from ...image import is_allowed_extension
 from ...cookies import get_cookies_dir
-from ...image.copy_images import secure_filename, get_source_url, images_dir
+from ...image.copy_images import secure_filename, get_source_url, get_media_dir
 from ... import ChatCompletion
 from ... import models
 from .api import Api
@@ -346,11 +346,12 @@ class Backend_Api(Api):
         @app.route('/search/<search>', methods=['GET'])
         def find_media(search: str):
             safe_search = [secure_filename(chunk.lower()) for chunk in search.split("+")]
-            if not os.access(images_dir, os.R_OK):
+            media_dir = get_media_dir()
+            if not os.access(media_dir, os.R_OK):
                 return jsonify({"error": {"message": "Not found"}}), 404
             if search not in self.match_files:
                 self.match_files[search] = {}
-                for root, _, files in os.walk(images_dir):
+                for root, _, files in os.walk(media_dir):
                     for file in files:
                         mime_type = is_allowed_extension(file)
                         if mime_type is not None:
@@ -438,7 +439,7 @@ class Backend_Api(Api):
     def get_provider_models(self, provider: str):
         api_key = request.headers.get("x_api_key")
         api_base = request.headers.get("x_api_base")
-        ignored = request.headers.get("x_ignored").split()
+        ignored = request.headers.get("x_ignored", "").split()
         models = super().get_provider_models(provider, api_key, api_base, ignored)
         if models is None:
             return "Provider not found", 404