refactor: streamline image param handling and fix media URL extraction

- Removed extension of `vision_models` into `text_models` in `PollinationsAI.get_models`
- Unified image parameter handling in `PollinationsAI.create_payload`, removing special case for `"gptimage"` model
- Added conditional inclusion of `"transparent"` and `"image"` params based on `transparent` flag and media content
- Replaced `quote_plus` with `quote` for URL encoding in query string construction
- In `OpenaiTemplate.create_payload`, wrapped media URL extraction in `iter()` to fix `next()` usage with list comprehension

g4f/Provider/template/OpenaiTemplate.py

@@ -94,7 +94,7 @@ class OpenaiTemplate(AsyncGeneratorProvider, ProviderModelMixin, RaiseErrorMixin
                 }
                 # Handle media if provided
                 if media is not None:
-                    data["image_url"] = next([data for data, _ in media if data and isinstance(data, str) and data.startswith("http://") or data.startswith("https://")], None)
+                    data["image_url"] = next(iter([data for data, _ in media if data and isinstance(data, str) and data.startswith("http://") or data.startswith("https://")]), None)
                 async with session.post(f"{api_base.rstrip('/')}/images/generations", json=data, ssl=cls.ssl) as response:
                     data = await response.json()
                     cls.raise_error(data, response.status)